1 | # assert-options
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2 |
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3 | Smart `options` handling, with one line of code:
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4 |
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5 | * throw detailed error on invalid options
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6 | * set default values for missing options
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7 |
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8 | Strongly-typed, built with TypeScript 4.x `strict` mode, for JavaScript clients.
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9 |
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10 | [![Build Status](https://travis-ci.org/vitaly-t/assert-options.svg?branch=master)](https://travis-ci.org/vitaly-t/assert-options)
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11 | [![Coverage Status](https://coveralls.io/repos/vitaly-t/assert-options/badge.svg?branch=master)](https://coveralls.io/r/vitaly-t/assert-options?branch=master)
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12 |
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13 | ## Rationale
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14 |
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15 | * Passing in invalid or misspelled option names is one of the most common errors in JavaScript.
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16 | * Assigning defaults is the most common operation for methods that take options.
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17 |
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18 | This module automates proper options handling - parsing and setting defaults where needed.
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19 |
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20 | Although this library is implemented in TypeScript, its objective is mainly to help JavaScript clients,
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21 | because TypeScript itself can handle invalid options and defaults natively.
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22 |
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23 | ## Installation
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24 |
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25 | ```
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26 | $ npm i assert-options
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27 | ```
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28 |
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29 | ## Usage
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30 |
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31 | ```js
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32 | const { assertOptions } = require('assert-options');
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33 |
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34 | function functionWithOptions(options) {
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35 | options = assertOptions(options, {first: 123, second: null});
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36 |
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37 | // options is a safe object here, with all missing defaults set.
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38 | }
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39 | ```
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40 |
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41 | When default values are not needed, you can just use an array of strings:
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42 |
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43 | ```js
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44 | function functionWithOptions(options) {
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45 | options = assertOptions(options, ['first', 'second']);
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46 |
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47 | // the result is exactly the same as using the following:
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48 | // options = assertOptions(options, {first: undefined, second: undefined});
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49 |
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50 | // options is a safe object here, without defaults.
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51 | }
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52 | ```
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53 |
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54 | ## API
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55 |
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56 | ### `assertOptions(options, defaults) => {}`
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57 |
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58 | * When `options` is `null`/`undefined`, new `{}` is returned, applying `defaults` as specified.
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59 |
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60 | * When `options` contains an unknown property, [Error] `Option "name" is not recognized.` is thrown.
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61 |
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62 | * When a property in `options` is missing or `undefined`, its value is set from the `defaults`,
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63 | provided it is available and its value is not `undefined`.
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64 |
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65 | * When `options` is not `null`/`undefined`, it must be of type `object`, or else [TypeError] is thrown:
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66 | `Invalid "options" parameter: value`.
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67 |
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68 | * Parameter `defaults` is required, as a non-`null` object or an array of strings, or else [TypeError]
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69 | is thrown: `Invalid "defaults" parameter: value`.
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70 |
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71 | [Error]:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error
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72 | [TypeError]:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
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