Here is my code JS :
var items = [255, 255, 255, 255];
items.forEach(function(item) {
if (item = 255) {
item = 0;
};
});
console.log(items)
In console.log I get [255, 255, 255, 255], why it doesn't change to [0, 0, 0, 0]? What am I doing wrong?
You want to use .map.
.forEach doesn't return anything, it is used to run a function with each item. .map returns a value for each iteration it runs.
var items = [255, 255, 255, 255]
items = items.map(item => item === 255 ? 0 : item)
console.log(items) // [0, 0, 0, 0]
Well, you are just changing the value type argument, nothing will happen with the items in the array. You can just change it to use map instead and create a new array
items = items.map( item => item === 255 ? 0 : item );
As remarked in the comments, in the original code, you also used an assignment operator instead of a compare operator
When you do:
if (item = 255)
You will assign item with 255 (which will be truthy, and then go into the if statement where you are assigning it with 0)
Your code contains two bugs.
= is assignment, not comparison. Your function is equivalent to:
function (item) {
item = 255;
item = 0;
}
item is a function parameter, i.e. a local variable in the anonymous function. Assigning to item has no effect on the items array:
var x = 255;
(function (y) { y = 0; })(x);
console.log(x);
// 255
You could take the reference to the array for changing the value inside of the callback for Array#forEach.
BTW, after a block statement, there is no need for a semicolon.
var items = [255, 255, 255, 255];
items.forEach(function(item, index, array) {
// ^^^^^
if (item = 255) {
array[index] = 0;
}
// ^ no semicolon needed
});
console.log(items);