如何使用 JavaScript 的 forEach 来修改数组的内容？

Question

给定一个 JavaScript 数组，如何使用forEach运算符修改数组中的项？

Answer 1

This is a simple question, but I'm posting the answer so I don't have to figure it out from scratch again. The function called by forEach takes three parameters, the current item, the index of that item, and the array object. So, using a => style function, the solution is:

var data = [1,2,3,4];
data.forEach( (item, i, self) => self[i] = item + 10 );

gives the result:

[11,12,13,14]

The self parameter isn't strictly necessary with the arrow style function, so

data.forEach( (item,i) => data[i] = item + 10);

also works. You also get the same result using a regular function, eg:

data.forEach( function(item, i, self) { self[i] = item + 10; } );

Answer 2

If you're replacing array items, a better way to do this is to use map instead:

var data = [1, 2, 3, 4];
data = data.map(item => item + 10);