time-to-botec

README.md (6274B)

---

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 # doUntilEachRight
 
 > Until a test condition is true, invoke a function for each element in a collection, iterating from right to left.
 
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 <section class="intro">
 
 </section>
 
 <!-- /.intro -->
 
 <!-- Package usage documentation. -->
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var doUntilEachRight = require( '@stdlib/utils/do-until-each-right' );
 ```
 
 #### doUntilEachRight( collection, fcn, predicate\[, thisArg ] )
 
 Invokes a `function` for each element in a `collection`, iterating from right to left, until either a `predicate` function returns `true` or the function has iterated over all `collection` elements. Note that the condition is evaluated **after** executing `fcn`; thus, `fcn` **always** executes at least once.
 
 ```javascript
 function predicate( value ) {
     return ( value !== value );
 }
 
 function log( value, index ) {
     console.log( '%s: %d', index, value );
 }
 
 var arr = [ 1, NaN, 2, 3, 4 ];
 
 doUntilEachRight( arr, log, predicate );
 /* =>
     4: 4
     3: 3
     2: 2
     1: NaN
 */
 ```
 
 Both the `predicate` function and the `function` to apply are provided three arguments:
 
 -   `value`: collection element
 -   `index`: collection index
 -   `collection`: input collection
 
 If provided an empty `collection`, both `value` and `index` are `undefined`.
 
 ```javascript
 function predicate( value ) {
     return ( value !== value );
 }
 
 function log( value, index ) {
     console.log( '%s: %s', index, value );
 }
 
 var arr = [];
 
 doUntilEachRight( arr, log, predicate );
 /* =>
     undefined: undefined
 */
 ```
 
 Basic support for dynamic collections is provided. Note, however, that index incrementation is **not** guaranteed to be monotonically **decreasing**.
 
 ```javascript
 var arr = [ 1, 2, 3, 4 ];
 var i = 0;
 
 function predicate( value ) {
     return ( value !== value );
 }
 
 function log1( value, index, collection ) {
     console.log( '%s: %d', index, value );
     i += 1;
     if ( index === 0 && collection.length < 10 ) {
         collection.unshift( i+1 );
     }
 }
 
 doUntilEachRight( arr, log1, predicate );
 /* =>
     3: 4
     2: 3
     1: 2
     0: 1
     0: 5
     0: 6
     0: 7
     0: 8
     0: 9
     0: 10
 */
 
 function log2( value, index, collection ) {
     console.log( '%s: %d', index, value );
     collection.pop();
 }
 
 arr = [ 1, 2, 3, 4 ];
 
 doUntilEachRight( arr, log2, predicate );
 /* =>
     3: 4
     1: 2
 */
 ```
 
 To set the function execution context for the applied function, provide a `thisArg`.
 
 ```javascript
 function predicate( value ) {
     return ( value < 3 );
 }
 
 function sum( value ) {
     this.sum += value;
     this.count += 1;
 }
 
 var arr = [ 1, NaN, 2, 3, 4 ];
 
 var context = {
     'sum': 0,
     'count': 0
 };
 
 doUntilEachRight( arr, sum, predicate, context );
 
 var mean = context.sum / context.count;
 // returns 3.0
 ```
 
 </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 returns the input `collection`.
 
 -   The function does **not** skip `undefined` elements.
 
     <!-- eslint-disable no-sparse-arrays -->
 
     ```javascript
     function predicate( value ) {
         return ( value !== value );
     }
 
     function log( value, index ) {
         console.log( '%s: %s', index, value );
     }
 
     var arr = [ 1, , , 4 ];
 
     doUntilEachRight( arr, log, predicate );
     /* =>
         3: 4
         2: undefined
         1: undefined
         0: 1
     */
     ```
 
 -   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 randu = require( '@stdlib/random/base/randu' );
 var floor = require( '@stdlib/math/base/special/floor' );
 var doUntilEachRight = require( '@stdlib/utils/do-until-each-right' );
 
 var arr;
 var i;
 var j;
 
 function predicate( value ) {
     return ( value !== value );
 }
 
 function log( value, index, collection ) {
     console.log( '%s: %d', index, value );
     i += 1;
     if ( isEven( i ) ) {
         collection.pop();
     } else {
         collection.unshift( i+1 );
     }
 }
 
 arr = new Array( 100 );
 j = floor( randu()*arr.length );
 for ( i = arr.length-1; i >= 0; i-- ) {
     if ( i === j ) {
         arr[ i ] = NaN;
     } else {
         arr[ i ] = i;
     }
 }
 
 i = 0;
 doUntilEachRight( arr, log, predicate );
 ```
 
 </section>
 
 <!-- /.examples -->
 
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 <section class="references">
 
 </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
 
 </section>
 
 <!-- /.links -->