I think you can writeconsole.log('')directly on the code and print the content to verify the order you guessed.

jquery’s animate is asynchronous, needless to say, http://www.cnblogs.com/aaronj...

The general principle is to use setTimeout and the like to delay execution regularly. Obviously, animate's callback will be placed in the task queue when the callback point is reached, somark2=falsemust be executed first

Calling move must be synchronously blocking,
animate is also synchronously blocking

$(document).ready(function () { var mark2 = true; if (mark2) { move(1); console.log('运行结束') } }) function move() { console.log("move start") $(".box").animate({ width: 50, height: 50, opacity: 30, left: 200, top: 200 }, { duration: 1500, start: function () { console.log("animate start") }, complete: function () { console.log("animate end") } }) console.log("move end") }

The result is

first:25 move start first:37 animate start first:44 move end first:20 运行结束 first:40 animate end

If move is not synchronous
You will see "Run End" first and then other things
If animate is not synchronous
You will see move end before animate start.
For example

$(document).ready(function () { var mark2 = true; if (mark2) { move(1); console.log('运行结束') } }) function move() { console.log("move start") setTimeout(function () { $(".box").animate({ width: 50, height: 50, opacity: 30, left: 200, top: 200 }, { duration: 1500, start: function () { console.log("animate start") }, complete: function () { console.log("animate end") } }) }, 500)

console.log("move end") }

The result is

first:25 move start first:45 move end first:20 运行结束 first:36 animate start first:39 animate end