time-to-botec

README.md (4473B)

---

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 # indexOf
 
 > Return the first index at which a given element can be found.
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var indexOf = require( '@stdlib/utils/index-of' );
 ```
 
 #### indexOf( arr, searchElement\[, fromIndex] )
 
 Returns the first index at which a given element can be found.
 
 ```javascript
 var arr = [ 4, 3, 2, 1 ];
 
 var idx = indexOf( arr, 3 );
 // returns 1
 ```
 
 If a `searchElement` is **not** present in an input `array`, the function returns `-1`.
 
 ```javascript
 var arr = [ 4, 3, 2, 1 ];
 
 var idx = indexOf( arr, 5 );
 // returns -1
 ```
 
 By default, the implementation searches an input `array` starting from the first element. To start searching from a different element, specify a `fromIndex`.
 
 ```javascript
 var arr = [ 1, 2, 3, 4, 5, 2, 6 ];
 
 var idx = indexOf( arr, 2, 3 );
 // returns 5
 ```
 
 If a `fromIndex` exceeds the input `array` length, the function returns `-1`.
 
 ```javascript
 var arr = [ 1, 2, 3, 4, 2, 5 ];
 
 var idx = indexOf( arr, 2, 10 );
 // returns -1
 ```
 
 If a `fromIndex` is less than `0`, the starting index is determined relative to the last index (with the last index being equivalent to `fromIndex = -1`).
 
 ```javascript
 var arr = [ 1, 2, 3, 4, 5, 2, 6, 2 ];
 
 var idx = indexOf( arr, 2, -4 );
 // returns 5
 
 idx = indexOf( arr, 2, -1 );
 // returns 7
 ```
 
 If `fromIndex` is less than `0` **and** its absolute value exceeds the input `array` length, the function searches the entire input `array`.
 
 ```javascript
 var arr = [ 1, 2, 3, 4, 5, 2, 6 ];
 
 var idx = indexOf( arr, 2, -10 );
 // returns 1
 ```
 
 The first argument is not limited to `arrays`, but may be any [array-like][@stdlib/assert/is-array-like] `object`.
 
 ```javascript
 var str = 'bebop';
 
 var idx = indexOf( str, 'o' );
 // returns 3
 ```
 
 </section>
 
 <!-- /.usage -->
 
 <section class="notes">
 
 ## Notes
 
 -   Search is performed using **strict equality** comparison. Thus,
 
     ```javascript
     var arr = [ 1, [ 1, 2, 3 ], 3 ];
 
     var idx = indexOf( arr, [ 1, 2, 3 ] );
     // returns -1
     ```
 
 -   This implementation is **not** [ECMAScript Standard][ecma-262] compliant. Notably, the [standard][ecma-262] specifies that an `array` be searched by calling `hasOwnProperty` (thus, for most cases, incurring a performance penalty), and the [standard][ecma-262] does **not** accommodate a `searchElement` equal to `NaN`. In this implementation, the following is possible:
 
     ```javascript
     // Locate the first element which is NaN...
     var arr = [ 1, NaN, 2, NaN ];
 
     var idx = indexOf( arr, NaN );
     // returns 1
 
     // Prototype properties may be searched as well...
     function Obj() {
         this[ 0 ] = 'beep';
         this[ 1 ] = 'boop';
         this[ 2 ] = 'woot';
         this[ 3 ] = 'bap';
         this.length = 4;
         return this;
     }
     Obj.prototype[ 2 ] = 'bop';
 
     var obj = new Obj();
 
     idx = indexOf( obj, 'bop' );
     // returns -1
 
     delete obj[ 2 ];
 
     idx = indexOf( obj, 'bop' );
     // returns 2
     ```
 
 </section>
 
 <!-- /.notes -->
 
 <section class="examples">
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```javascript
 var indexOf = require( '@stdlib/utils/index-of' );
 
 var arr;
 var obj;
 var str;
 var idx;
 var i;
 
 // Arrays...
 arr = new Array( 10 );
 for ( i = 0; i < arr.length; i++ ) {
     arr[ i ] = i * 10;
 }
 idx = indexOf( arr, 40 );
 
 console.log( idx );
 // => 4
 
 // Array-like objects...
 obj = {
     '0': 'beep',
     '1': 'boop',
     '2': 'bap',
     '3': 'bop',
     'length': 4
 };
 
 idx = indexOf( obj, 'bap' );
 
 console.log( idx );
 // => 2
 
 // Strings...
 str = 'beepboopbop';
 
 idx = indexOf( str, 'o' );
 
 console.log( idx );
 // => 5
 ```
 
 </section>
 
 <!-- /.examples -->
 
 <section class="links">
 
 [ecma-262]: http://www.ecma-international.org/ecma-262/6.0/#sec-array.prototype.indexof
 
 [@stdlib/assert/is-array-like]: https://www.npmjs.com/package/@stdlib/assert-is-array-like
 
 </section>
 
 <!-- /.links -->