time-to-botec

README.md (5059B)

---

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 # forEach
 
 > Invoke a function for each element in a collection.
 
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 <section class="intro">
 
 </section>
 
 <!-- /.intro -->
 
 <!-- Package usage documentation. -->
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var forEach = require( '@stdlib/utils/for-each' );
 ```
 
 #### forEach( collection, fcn\[, thisArg ] )
 
 Invokes a `function` for each element in a `collection`.
 
 ```javascript
 function log( value, index ) {
     console.log( '%s: %d', index, value );
 }
 
 var arr = [ 1, 2, 3, 4 ];
 
 forEach( arr, log );
 /* =>
     0: 1
     1: 2
     2: 3
     3: 4
 */
 ```
 
 The invoked `function` is provided three arguments:
 
 -   `value`: collection element
 -   `index`: collection index
 -   `collection`: input collection
 
 Basic support for dynamic collections is provided. Note, however, that index incrementation is monotonically increasing.
 
 ```javascript
 function log1( value, index, collection ) {
     console.log( '%s: %d', index, value );
     if ( index === collection.length-1 && collection.length < 10 ) {
         collection.push( index+2 );
     }
 }
 
 var arr = [ 1, 2, 3, 4 ];
 
 forEach( arr, log1 );
 /* =>
     0: 1
     1: 2
     2: 3
     3: 4
     4: 5
     5: 6
     6: 7
     7: 8
     8: 9
     9: 10
 */
 
 function log2( value, index, collection ) {
     console.log( '%s: %d', index, value );
     collection.shift();
 }
 
 arr = [ 1, 2, 3, 4 ];
 
 forEach( arr, log2 );
 /* =>
     0: 1
     1: 3
 */
 ```
 
 To set the function execution context, provide a `thisArg`.
 
 ```javascript
 function sum( value ) {
     this.sum += value;
     this.count += 1;
 }
 
 var arr = [ 1, 2, 3, 4 ];
 
 var context = {
     'sum': 0,
     'count': 0
 };
 
 forEach( arr, sum, context );
 
 var mean = context.sum / context.count;
 // returns 2.5
 ```
 
 </section>
 
 <!-- /.usage -->
 
 <!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
 
 <section class="notes">
 
 ## Notes
 
 -   A `collection` may be either an [`Array`][mdn-array], [`Typed Array`][mdn-typed-array], or an array-like [`Object`][mdn-object] (excluding `strings` and `functions`).
 
 -   The function differs from [`Array.prototype.forEach`][mdn-array-foreach] in the following ways:
 
     -   The function returns the input `collection`.
 
     -   The function does **not** skip `undefined` elements.
 
         <!-- eslint-disable no-sparse-arrays -->
 
         ```javascript
         function log( value, index ) {
             console.log( '%s: %s', index, value );
         }
 
         var arr = [ 1, , , 4 ];
 
         forEach( arr, log );
         /* =>
             0: 1
             1: undefined
             2: undefined
             3: 4
         */
         ```
 
     -   The function provides limited support for dynamic collections (i.e., collections whose `length` changes during execution).
 
 </section>
 
 <!-- /.notes -->
 
 <!-- Package usage examples. -->
 
 <section class="examples">
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```javascript
 var isEven = require( '@stdlib/assert/is-even' ).isPrimitive;
 var forEach = require( '@stdlib/utils/for-each' );
 
 function log( value, index, collection ) {
     console.log( '%s: %d', index, value );
     if ( isEven( index ) ) {
         collection.shift();
     } else {
         collection.push( index+1 );
     }
 }
 
 var arr;
 var i;
 
 arr = new Array( 100 );
 for ( i = 0; i < arr.length; i++ ) {
     arr[ i ] = i;
 }
 
 forEach( arr, log );
 ```
 
 </section>
 
 <!-- /.examples -->
 
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 </section>
 
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 <section class="links">
 
 [mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array
 
 [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
 
 [mdn-object]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object
 
 [mdn-array-foreach]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach
 
 </section>
 
 <!-- /.links -->