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>