time-to-botec

README.md (8250B)

---

 <!--
 
 @license Apache-2.0
 
 Copyright (c) 2018 The Stdlib Authors.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
    http://www.apache.org/licenses/LICENSE-2.0
 
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 See the License for the specific language governing permissions and
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 # Merge
 
 > Merge and extend objects.
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var merge = require( '@stdlib/utils/merge' );
 ```
 
 #### merge( target, source1\[, source2\[,...,sourceN]] )
 
 Merges and extends a target `object`.
 
 ```javascript
 var target = {
     'a': 'beep'
 };
 var source = {
     'a': 'boop',
     'b': 'bap'
 };
 
 var out = merge( target, source );
 /* returns
     {
         'a': 'boop',
         'b': 'bap'
     }
 */
 ```
 
 The function supports merging multiple source `objects`.
 
 ```javascript
 var target = {
     'a': 'beep'
 };
 var source1 = {
     'b': 'boop'
 };
 var source2 = {
     'c': 'cat'
 };
 
 var out = merge( target, source1, source2 );
 /* returns
     {
         'a': 'beep',
         'b': 'boop',
         'c': 'cat'
     }
 */
 ```
 
 #### merge.factory( options )
 
 Returns a custom merge `function` for merging and extending `objects`.
 
 ```javascript
 var opts = {
     'level': 100,
     'copy': true,
     'override': true,
     'extend': true
 };
 
 var m = merge.factory( opts );
 ```
 
 The function accepts the following `options`:
 
 -   **level**: limits the merge depth. The default merge strategy is a deep (recursive) merge. Default: `+infinity`.
 -   **copy**: `boolean` indicating whether to [deep copy][@stdlib/utils/copy] merged values. Deep copying prevents shared references and source `object` mutation. Default: `true`.
 -   **override**: defines the merge strategy. If `true`, source `object` values will **always** override target `object` values. If `false`, source values **never** override target values (useful for adding, but not overwriting, properties). To define a custom merge strategy, provide a `function`. Default: `true`.
 -   **extend**: `boolean` indicating whether new properties can be added to the target `object`. If `false`, only **shared** properties are merged. Default: `true`.
 
 The default merge is a deep (recursive) merge.
 
 ```javascript
 var m = merge.factory( {} );
 
 var target = {
     'a': {
         'b': {
             'c': 5
         },
         'd': 'beep'
     }
 };
 var source = {
     'a': {
         'b': {
             'c': 10
         }
     }
 };
 
 var out = m( target, source );
 /* returns
     {
         'a': {
             'b': {
                 'c': 10
             },
             'd': 'beep'
         }
     }
 */
 ```
 
 To limit the merge depth, set the `level` option.
 
 ```javascript
 var m = merge.factory({
     'level': 2
 });
 
 var target = {
     '1': {
         'a': 'beep',
         '2': {
             '3': null,
             'b': [ 5, 6, 7 ]
         }
     }
 };
 
 var source = {
     '1': {
         'b': 'boop',
         '2': {
             '3': [ 1, 2, 3 ]
         }
     }
 };
 
 var out = m( target, source );
 /* returns
     {
         '1': {
             'a': 'beep',
             'b': 'boop',
             '2': {
                 '3': [ 1, 2, 3 ]
             }
         }
     }
 */
 ```
 
 By default, merged values are [deep copied][@stdlib/utils/copy].
 
 ```javascript
 var m = merge.factory( {} );
 
 var target = {
     'a': null
 };
 var source = {
     'a': {
         'b': [ 1, 2, 3 ]
     }
 };
 
 var out = m( target, source );
 
 console.log( out.a.b === source.a.b );
 // => false
 ```
 
 To allow shared references, set the `copy` option to `false`.
 
 ```javascript
 var m = merge.factory({
     'copy': false
 });
 
 var target = {};
 
 var source = {
     'a': [ 1, 2, 3 ]
 };
 
 var out = m( target, source );
 
 var bool = ( out.a === source.a );
 // returns true
 ```
 
 To prevent existing properties from being overridden, set the `override` option to `false`.
 
 ```javascript
 var m = merge.factory({
     'override': false
 });
 
 var target = {
     'a': 'beep',
     'b': 'boop'
 };
 
 var source = {
     'a': null,
     'c': 'bop'
 };
 
 var out = m( target, source );
 /* returns
     {
         'a': 'beep',
         'b': 'boop',
         'c': 'bop'
     }
 */
 ```
 
 Alternatively, to define a custom merge strategy, set the `override` option to a `function`.
 
 ```javascript
 function strategy( a, b, key ) {
     /* Parameters:
         a => target value
         b => source value
         key => object key
     */
     if ( key === 'a' ) {
         return b;
     }
     if ( key === 'b' ) {
         return a;
     }
     return 'bebop';
 }
 
 var m = merge.factory({
     'override': strategy
 });
 
 var target = {
     'a': 'beep',
     'b': 'boop',
     'c': 1234
 };
 
 var source = {
     'a': null,
     'b': {},
     'c': 'bop'
 };
 
 var out = m( target, source );
 /* returns
     {
         'a': null,
         'b': 'boop',
         'c': 'bebop'
     }
 */
 ```
 
 To prevent non-existent properties from being added to the target `object`, set the `extend` option to `false`.
 
 ```javascript
 var m = merge.factory({
     'extend': false
 });
 
 var target = {
     'a': 'beep',
     'b': 'boop'
 };
 
 var source = {
     'b': 'hello',
     'c': 'world'
 };
 
 var out = m( target, source );
 /* returns
     {
         'a': 'beep',
         'b': 'hello'
     }
 */
 ```
 
 </section>
 
 <!-- /.usage -->
 
 <section class="notes">
 
 * * *
 
 ## Notes
 
 -   The target `object` is **mutated**.
 
     ```javascript
     var target = {
         'a': 'beep'
     };
     var source = {
         'b': 'boop'
     };
 
     var out = merge( target, source );
 
     console.log( out === target );
     // => true
 
     console.log( target.b );
     // => 'boop'
     ```
 
     To return a new `object`, provide an empty `object` as the first argument.
 
     ```javascript
     var target = {
         'a': 'beep'
     };
     var source = {
         'b': 'boop'
     };
 
     var out = merge( {}, target, source );
 
     console.log( out === target );
     // => false
     ```
 
 -   **Only** plain JavaScript `objects` are merged and extended. The following values/types are either [deep copied][@stdlib/utils/copy] or assigned:
 
     -   `Boolean`
     -   `String`
     -   `Number`
     -   `Date`
     -   `RegExp`
     -   `Array`
     -   `Int8Array`
     -   `Uint8Array`
     -   `Uint8ClampedArray`
     -   `Init16Array`
     -   `Uint16Array`
     -   `Int32Array`
     -   `Uint32Array`
     -   `Float32Array`
     -   `Float64Array`
     -   `Buffer` ([Node.js][node-buffer])
     -   `Set`
     -   `Map`
     -   `Error`
     -   `URIError`
     -   `ReferenceError`
     -   `SyntaxError`
     -   `RangeError`
 
 -   Support for deep merging class instances is inherently [**fragile**][@stdlib/utils/copy].
 
 -   `Number`, `String`, or `Boolean` objects are merged as [primitives][@stdlib/utils/copy].
 
 -   Functions are **not** [deep copied][@stdlib/utils/copy].
 
 </section>
 
 <!-- /.notes -->
 
 <section class="examples">
 
 * * *
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```javascript
 var merge = require( '@stdlib/utils/merge' );
 
 var target;
 var source;
 var out;
 
 target = {
     'a': 'beep',
     'b': 'boop',
     'c': {
         'c1': 'woot',
         'c2': false,
         'c3': {
             'c3a': [ 1, 2 ],
             'c3b': null
         }
     },
     'd': [ 1, 2, 3 ]
 };
 
 source = {
     'b': 3.141592653589793,
     'c': {
         'c1': 'bap',
         'c3': {
             'c3b': 5,
             'c3c': 'bop'
         },
         'c4': 1337,
         'c5': new Date()
     },
     'd': [ 4, 5, 6 ],
     'e': true
 };
 
 out = merge( {}, target, source );
 /* returns
     {
         'a': 'beep',
         'b': 3.141592653589793,
         'c': {
             'c1': 'bap',
             'c2': false,
             'c3': {
                 'c3a': [ 1, 2 ],
                 'c3b': 5,
                 'c3c': 'bop'
             },
             'c4': 1337,
             'c5': <Date>
         },
         'd': [ 4, 5, 6 ],
         'e': true
     }
 */
 ```
 
 </section>
 
 <!-- /.examples -->
 
 <section class="links">
 
 [@stdlib/utils/copy]: https://www.npmjs.com/package/@stdlib/utils/tree/main/copy
 
 [node-buffer]: http://nodejs.org/api/buffer.html
 
 </section>
 
 <!-- /.links -->