functions

This block provides an object with a set of methods for working with JavaScript functions.

Overview

Properties and methods of the object

Elements of the block

Public block technologies

The block is implemented in:

• vanilla.js

Description

Properties and methods of the object

isFunction method

Checks whether a passed argument is a function.

Accepted arguments:

• obj {*} – The object being checked. Required argument.

Return value: Boolean. If the argument is a function, then true.

modules.require('functions', function(func) {
    var a = function(){},
        b = {};
    console.log(func.isFunction(a)); //true
    console.log(func.isFunction(b)); //false
});

noop property

Empty function (function() {}).

No arguments or return value.

You can use noop when you need a function but there isn't a reason to add the logic. For example, you can use it as a placeholder for base classes at the design stage when using OOP.

Example:

modules.define('base-class', ['inherit', 'functions'], function(provide, inherit, functions) {

provide(inherit({
    getData : function() {
        this._sendRequest();
    },

    _sendRequest : functions.noop

}));

});

Elements of the block

The block elements implement a set of function decorators.

The decorators add logic to the function without changing its original signature.

debounce element

A decorator that postpones function calls for the specified delay time. After each attempt to make a call, the delay starts over again.

Accepted arguments:

• fn {Function} — Original function. Required argument.
• timeout {Number} — Time of delay, in milliseconds. Required argument.
• [invokeAsap {Boolean}] — The debounce mode. By default, the first mode is used (corresponding to the false value).
• [context {Object}] — The context for executing the original function.

There are two debounce modes, depending on the value of invokeAsap:

1. The original function is called when the delay expires after the last call attempt.
2. The original function is first called as soon as the decorated function is called. After this, the behavior is the same as in the first mode.

Return value: Function. The decorated function.

Example:

modules.require('functions__debounce', function(provide, debounce) {

    function log() {
        console.log('hello!');
    }

    var debouncedLog = debounce(log, 300);
    setInterval(debouncedLog, 50);

});

throttle element

This decorator allows you to "slow down" the function. It won't be executed more than once during the specified period, no matter how many times it is called during this time. All calls in the meantime are ignored.

Accepted arguments:

• fn {Function} — Original function. Required argument.
• period {Number} — The interval between calls, in milliseconds. Required argument.
• [context {Object}] — The context for executing the original function.

Return value: Function. The decorated function.

This method is convenient for setting resource-intensive handlers for frequently generated events, such as resize, pointermove, and so on.

Example:

modules.require('functions__throttle', function(provide, throttle) {

    function log() {
        console.log('hello!');
    }

    var throttledLog = throttle(log, 300);
    setInterval(throttledLog, 50);

});

As a result, the function is executed no more than once every 300 milliseconds.