在 jQuery 输入字段事件处理中链接焦点（）和模糊（）？

Question

In jQuery i've seen the blur( ) chained to the focus( ) like this:

$("input").focus(function(){
    $(this).css("background-color", "blue");
}).blur(function(){
    $(this).css("background-color", "red");
});

Why doesn't blur( ) execute immediately after the focus event is fired? When blur( ) is chained to focus( ) it doesn't execute until after the field loses focus yet because it is chained I would think it would fire immediately after the focus event is fired even though the input field has not yet lost focus.

Answer 1

when chaining non-event functions they always execute in quick succession

In this case, they functions are running immediately, but these functions are event bindings , not the events .

So the blur event is not chained to the focus event, only the event handlers are added via chaining.

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Note that chaining just allows for functions to be called one after the other without interim variables. There's no difference in your code from:

var inp = $("input");
inp.focus(function() { $(this).css("background-color", "blue"); });
inp.blur(function() { $(this).css("background-color", "red"); });