| 1 |
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| 2 | let evaluate = (instance, field, props) => {
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| 3 | let evaluator = instance[field.type];
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| 4 | return typeof evaluator === 'function' && evaluator.call(instance, field, props);
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| 5 | };
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| 6 |
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| 7 | /**
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| 8 | * @typedef LogicalOperator
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| 9 | * @property {string} type
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| 10 | * @property {Array.<LogicalOperator|ComparisonOperator>} fields
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| 11 | */
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| 12 |
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| 13 | /**
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| 14 | * @typedef ComparisonOperator
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| 15 | * @property {string} type
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| 16 | * @property {string} key
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| 17 | * @property {string|number|boolean} value
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| 18 | */
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| 19 |
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| 20 | /**
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| 21 | * expression evaluator will parse logical and comparison operators
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| 22 | */
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| 23 | class ExpressionEvaluator {
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| 24 |
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| 25 | /**
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| 26 | * expects a single logical operator or comparison operator
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| 27 | * @param {ComparisonOperator|LogicalOperator} q
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| 28 | * @param {*} props
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| 29 | */
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| 30 | evaluate(q, props) {
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| 31 | if (q === null || q === undefined) {
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| 32 | return true;
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| 33 | }
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| 34 | if (q.hasOwnProperty('type')) {
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| 35 | return evaluate(this, q, props);
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| 36 | } else {
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| 37 | return true;
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| 38 | }
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| 39 | }
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| 40 |
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| 41 | /**
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| 42 | *
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| 43 | * @param {LogicalOperator} query
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| 44 | * @param {*} props
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| 45 | * @returns {boolean}
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| 46 | */
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| 47 | and(query, props) {
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| 48 | return query.fields.every(field => evaluate(this, field, props));
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| 49 | }
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| 50 | /**
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| 51 | *
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| 52 | * @param {LogicalOperator} query
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| 53 | * @param {*} props
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| 54 | * @returns {boolean}
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| 55 | */
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| 56 | or(query, props) {
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| 57 | return query.fields.some(field => evaluate(this, field, props));
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| 58 | }
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| 59 | /**
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| 60 | *
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| 61 | * @param {ComparisonOperator} field
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| 62 | * @param {*} props
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| 63 | * @returns {boolean}
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| 64 | */
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| 65 | eq(field, props) {
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| 66 | return field.value === props[field.key];
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| 67 | }
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| 68 |
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| 69 | /**
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| 70 | *
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| 71 | * @param {ComparisonOperator} field
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| 72 | * @param {*} props
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| 73 | * @returns {boolean}
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| 74 | */
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| 75 | neq(field, props) {
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| 76 | return field.value !== props[field.key];
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| 77 | }
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| 78 | }
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| 79 |
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| 80 | module.exports = new ExpressionEvaluator();
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