Count the number of elements in an array which pass a test implemented by a predicate function.
var countIf = require( '@stdlib/array/base/count-if' );Counts the number of elements in an array which pass a test implemented by a predicate function.
function predicate( value ) {
return ( value > 0 );
}
var x = [ 0, 1, 0, 1, 2 ];
var out = countIf( x, predicate );
// returns 3The predicate function is provided three arguments:
- value: current array element.
- index: current array element index.
- arr: input array.
To set the predicate function execution context, provide a thisArg.
function predicate( value ) {
this.count += 1;
return ( value > 0 );
}
var x = [ 0, 1, 0, 1, 2 ];
var context = {
'count': 0
};
var out = countIf( x, predicate, context );
// returns 3
var cnt = context.count;
// returns 5var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive;
var naryFunction = require( '@stdlib/utils/nary-function' );
var countIf = require( '@stdlib/array/base/count-if' );
var x = discreteUniform( 10, -5, 5, {
'dtype': 'int32'
});
// returns <Int32Array>
var out = countIf( x, naryFunction( isPositiveInteger, 1 ) );
// returns <number>
console.log( x );
console.log( out );