time-to-botec/js/node_modules/@stdlib/utils/every-by/README.md

everyBy

Test whether all elements in a collection pass a test implemented by a predicate function.

Usage

var everyBy = require( '@stdlib/utils/every-by' );

everyBy( collection, predicate[, thisArg ] )

Tests whether all elements in a collection pass a test implemented by a predicate function.

function isPositive( value ) {
    return ( value > 0 );
}

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

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

If a predicate function returns a non-truthy value, the function immediately returns false.

function isPositive( value ) {
    return ( value > 0 );
}

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

var bool = everyBy( arr, isPositive );
// returns false

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

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

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

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

var mean = context.sum / context.count;
// returns 2.5

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 true.

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

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

  • The function does not skip undefined elements.

    function log( value, index ) {
        console.log( '%s: %s', index, value );
        return true;
    }
    
    var arr = [ 1, , , 4 ];
    
    var bool = everyBy( 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).

Examples

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

function isPositive( value ) {
    return ( value > 0 );
}

var bool;
var arr;
var i;

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

bool = everyBy( arr, isPositive );
// returns <boolean>