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7 |
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8 | var resolve = require('./resolve')
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9 | var isObservable = require('./is-observable')
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10 | var isSame = require('./lib/is-same')
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11 | var onceIdle = require('./once-idle')
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12 |
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13 | module.exports = computed
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14 |
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15 | computed.NO_CHANGE = {}
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16 | computed.extended = extendedComputed
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17 |
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18 | function computed (observables, lambda, opts) {
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19 |
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20 | var instance = new ProtoComputed(observables, lambda, opts)
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21 | return instance.MutantComputed.bind(instance)
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22 | }
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23 |
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24 |
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25 | function ProtoComputed (observables, lambda, opts) {
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26 | if (!Array.isArray(observables)) {
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27 | observables = [observables]
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28 | }
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29 | this.values = []
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30 | this.releases = []
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31 | this.computedValue = null
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32 | this.outputValue = null
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33 | this.inner = null
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34 | this.updating = false
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35 | this.live = false
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36 | this.lazy = false
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37 | this.initialized = false
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38 | this.listeners = []
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39 | this.observables = observables
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40 | this.lambda = lambda
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41 | this.opts = opts
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42 | this.comparer = opts && opts.comparer || null
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43 | this.context = opts && opts.context || {}
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44 | this.boundOnUpdate = this.onUpdate.bind(this)
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45 | this.boundUpdateNow = this.updateNow.bind(this)
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46 | }
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47 |
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48 | ProtoComputed.prototype = {
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49 | MutantComputed: function (listener) {
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50 | if (!listener) {
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51 | return this.getValue()
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52 | }
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53 |
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54 | if (typeof listener !== 'function') {
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55 | throw new Error('Listeners must be functions.')
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56 | }
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57 |
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58 | this.listeners.push(listener)
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59 | this.listen()
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60 |
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61 | return this.removeListener.bind(this, listener)
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62 | },
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63 | removeListener: function (listener) {
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64 | for (var i = 0, len = this.listeners.length; i < len; i++) {
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65 | if (this.listeners[i] === listener) {
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66 | this.listeners.splice(i, 1)
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67 | break
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68 | }
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69 | }
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70 | if (!this.listeners.length) {
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71 | this.unlisten()
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72 | }
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73 | },
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74 | listen: function () {
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75 | if (!this.live) {
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76 | for (var i = 0, len = this.observables.length; i < len; i++) {
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77 | if (isObservable(this.observables[i])) {
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78 | this.releases.push(this.observables[i](this.boundOnUpdate))
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79 | }
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80 | }
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81 | if (this.inner) {
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82 | this.releaseInner = this.inner(this.onInnerUpdate.bind(this, this.inner))
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83 | }
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84 | this.live = true
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85 | this.lazy = true
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86 |
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87 | if (this.opts && this.opts.onListen) {
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88 | var release = this.opts.onListen()
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89 | if (typeof release === 'function') {
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90 | this.releases.push(release)
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91 | }
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92 | }
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93 | }
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94 | },
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95 | unlisten: function () {
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96 | if (this.live) {
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97 | this.live = false
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98 |
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99 | if (this.releaseInner) {
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100 | this.releaseInner()
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101 | this.releaseInner = null
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102 | }
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103 |
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104 | while (this.releases.length) {
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105 | this.releases.pop()()
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106 | }
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107 |
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108 | if (this.opts && this.opts.onUnlisten) {
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109 | this.opts.onUnlisten()
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110 | }
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111 | }
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112 | },
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113 | update: function () {
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114 | var changed = false
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115 | for (var i = 0, len = this.observables.length; i < len; i++) {
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116 | var newValue = resolve(this.observables[i])
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117 | if (!isSame(newValue, this.values[i], this.comparer)) {
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118 | changed = true
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119 | this.values[i] = newValue
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120 | }
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121 | }
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122 |
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123 | if (changed || !this.initialized) {
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124 | this.initialized = true
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125 | var newComputedValue = this.lambda.apply(this.context, this.values)
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126 |
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127 | if (newComputedValue === computed.NO_CHANGE) {
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128 | return false
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129 | }
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130 |
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131 | if (!isSame(newComputedValue, this.computedValue, this.comparer)) {
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132 | if (this.releaseInner) {
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133 | this.releaseInner()
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134 | this.inner = this.releaseInner = null
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135 | }
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136 |
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137 | this.computedValue = newComputedValue
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138 |
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139 | if (isObservable(newComputedValue)) {
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140 |
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141 | this.outputValue = newComputedValue()
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142 | this.inner = newComputedValue
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143 | if (this.live) {
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144 | this.releaseInner = this.inner(this.onInnerUpdate.bind(this, this.inner))
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145 | }
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146 | } else {
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147 | this.outputValue = this.computedValue
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148 | }
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149 | return true
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150 | }
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151 | }
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152 | return false
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153 | },
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154 | onUpdate: function () {
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155 | if (this.opts && this.opts.idle) {
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156 | if (!this.updating) {
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157 | this.updating = true
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158 | onceIdle(this.boundUpdateNow)
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159 | }
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160 | } else if (this.opts && this.opts.nextTick) {
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161 | if (!this.updating) {
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162 | this.updating = true
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163 | setImmediate(this.boundUpdateNow)
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164 | }
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165 | } else {
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166 | this.updateNow()
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167 | }
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168 | },
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169 | onInnerUpdate: function (obs, value) {
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170 | if (obs === this.inner) {
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171 | if (!isSame(value, this.outputValue, this.comparer)) {
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172 | this.outputValue = value
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173 | this.broadcast()
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174 | }
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175 | }
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176 | },
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177 | updateNow: function () {
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178 | this.updating = false
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179 | if (this.update()) {
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180 | this.broadcast()
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181 | }
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182 | },
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183 | getValue: function () {
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184 | if (!this.live || this.lazy || this.updating) {
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185 | this.lazy = false
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186 | if (this.opts && this.opts.nextTick && this.live && this.lazy) {
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187 | this.onUpdate()
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188 | } else {
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189 | this.update()
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190 | }
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191 | if (this.inner) {
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192 | this.outputValue = resolve(this.inner)
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193 | }
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194 | }
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195 | return this.outputValue
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196 | },
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197 | broadcast: function () {
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198 |
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199 | var listeners = this.listeners.slice(0)
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200 | for (var i = 0, len = listeners.length; i < len; i++) {
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201 | listeners[i](this.outputValue)
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202 | }
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203 | }
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204 | }
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205 |
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206 | function extendedComputed (observables, update) {
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207 | var live = false
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208 | var lazy = false
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209 |
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210 | var instance = computed(observables, function () {
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211 | return update()
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212 | }, {
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213 | onListen: function () { live = lazy = true },
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214 | onUnlisten: function () { live = false }
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215 | })
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216 |
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217 | instance.checkUpdated = function () {
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218 | if (!live || lazy) {
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219 | lazy = false
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220 | update()
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221 | }
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222 | }
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223 |
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224 | return instance
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225 | }
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