jquery - What this JavaScript function method called? -

i quite interested when run simple function

$(window).resize(function() {     var = $(this);     var widthvalue = that.width();      console.log(widthvalue + 'px'); }); 

it works when start resizing browser window.

but when this

$(window).resize(function() {     var = $(this);     var widthvalue = that.width();      console.log(widthvalue + 'px'); }).resize(); 

it acts load();. added resize() @ end.

what called? not sure understand why , how works.

the technique called chaining.

it boils down function returning this @ end, can call method of same object chaining method calls 1 after other.

var foo = {   count: 0,   up: function () { this.count++; return this; },   show: function () { alert(this.count); return this; } }  foo.show().up().show().up().up().show(); 

in particular example, resize method overloaded. if give function argument bind function event handler. if call without arguments, trigger event instead.