JS = a new JS function notation found today

Source: Internet
Author: User

Today in the online tour to a notation, return the number of letters in the string

var arr= ' AAABBCCAA '; var info = arr.split ("). reduce (p, k) = (p[k]++ | | (P[k] = 1), p), {}); Console.log (info) ;

Get: Object {a:5, b:2, C:2}

Reduce I found it is es5 new Add the array function, here do not elaborate, interested in their own search;

The key is ' = ', is the first time I saw in JS, in the online search did not find any information, I understand it, I hope the great God.

Should be an anonymous function, similar to () = (), this, before () for the input, after () for the output;

Test:

var kk= (A, a, b) = (A +); KK (2,6);

After execution, get 8;

Can also be written as:

var k=a=>Alert (a); K (0);

Alert Popup 0;

Is there a great God to tell me more about this and what is it?

JS = a new JS function notation found today

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