用Javascript对数组进行数字排序

Question

Hello,

i am new to stackoverflow and coding so I hope you don't mind me asking such a trivial question.

I learned that sorting an array numerically is done as follows. I am also aware of the simpler ES6 version.

 var ax = [], bx = []; function sortNumber (a, b) { ax.push(a); bx.push(b); return ab; } var numArray = [140000, 104, 99, 2]; numArray.sort(sortNumber); console.log('array=' + numArray); console.log('a=' + ax); console.log('b=' + bx); 

What i don't understand is, why for example in my Code-Example in the sortNumber function

a = [140000, 104, 140000, 104, 99] and b = [99, 99, 2, 2, 2] ?

Can someone tell my how a and b are determined?

Thanks in advance!

Answer 1

Can someone tell my how a and b are determined?

It's entirely up to the JavaScript engine's implementation of sort . All that the specification tells us is that they'll be entries from the array that need to be compared so the sort algorithm can do its job.

If you like, you can see V8's implementation here , which is a variation of a TimSort . (V8 is the JavaScript engine used in Chromium, Chrome, Brave, and Node.js.)

I should note that V8 doesn't use the values for a and b that are shown in your question, it uses 104 , 99 , and 2 for a and 140000 , 104 , and 99 for b .

You can see which ones the JavaScript engine in your current browser uses here:

 var avalues = []; var bvalues = [] function sortNumber (a, b) { console.log("a = " + a + ", b = " + b); avalues.push(a); bvalues.push(b); return ab; } var numArray = [140000, 104, 99, 2]; numArray.sort(sortNumber); console.log("done, result:", numArray.join(", ")); console.log("a values: ", avalues.join(", ")); console.log("b values: ", bvalues.join(", ")); 

Answer 2

I think your question is how this sorting function is working.

1. Sort functions requires comparison function (Like on what basis you need to sort the array. It can be anything)
2. Above in sortNumber function, a and b are nothing but the two values of the numArray. Example - when you call numArray.sort(sortNumber) ; it will call on all the elements of the array with each other (You care comparing each element). if a - b > 0 , a is greater than b. if a - b < 0 , b is greater than a. if a - b = 0 , both are equal. This condition will get checked on all the elements [140000, 104, 99, 2].

Hope this helps.

Answer 3

在这种情况下，我只是使用lodash。

_.sortBy([140000, 104, 99, 2]) // => [2, 99, 104, 140000]