time-to-botec/squiggle/node_modules/@stdlib/utils/any-by

anyBy

Test whether at least one element in a collection passes a test implemented by a predicate function.

Usage

var anyBy = require( '@stdlib/utils/any-by' );

anyBy( collection, predicate[, thisArg ] )

Tests whether at least one element in a collection passes a test implemented by a predicate function.

function isNegative( value ) {
    return ( value < 0 );
}

var arr = [ 1, 2, 3, 4, -1 ];

var bool = anyBy( arr, isNegative );
// returns true

If a predicate function returns a truthy value, the function immediately returns true.

function isPositive( value ) {
    if ( value < 0 ) {
        throw new Error( 'should never reach this line' );
    }
    return ( value > 0 );
}

var arr = [ 1, -2, 3, 4 ];

var bool = anyBy( arr, isPositive );
// returns true

The invoked function is provided three arguments:

• value: collection element
• index: collection index
• collection: input collection

To set the function execution context, provide a thisArg.

function sum( value ) {
    this.sum += value;
    this.count += 1;
    return ( value < 0 );
}

var arr = [ 1, 2, 3, 4, -5 ];

var context = {
    'sum': 0,
    'count': 0
};

var bool = anyBy( arr, sum, context );
// returns true

var mean = context.sum / context.count;
// returns 1.0

Notes

• A collection may be either an Array, Typed Array, or an array-like Object (excluding strings and functions).

• If provided an empty collection, the function returns false.

  function alwaysTrue() {
      return true;
  }
  var bool = anyBy( [], alwaysTrue );
  // returns false
  

• The function differs from Array.prototype.some in the following ways:

  • The function does not skip undefined elements.

    function log( value, index ) {
        console.log( '%s: %s', index, value );
        return ( value < 0 );
    }
    
    var arr = [ 1, , , 4, -1 ];
    
    var bool = anyBy( arr, log );
    /* =>
        0: 1
        1: undefined
        2: undefined
        3: 4
        4: -1
    */
    

  • The function provides limited support for dynamic collections (i.e., collections whose length changes during execution).

Examples

var randu = require( '@stdlib/random/base/randu' );
var anyBy = require( '@stdlib/utils/any-by' );

function threshold( value ) {
    return ( value > 0.95 );
}

var bool;
var arr;
var i;

arr = [];
for ( i = 0; i < 100; i++ ) {
    arr.push( randu() );
}

bool = anyBy( arr, threshold );
// returns <boolean>