How to iterate over an array and remove elements in JavaScript

I have an array of elements and need to remove certain ones from it. The problem is that JavaScript doesn't seem to have a for each loop and if I use a for loop I run into problems with it basically trying to check elements beyond the bounds of the array, or missing elements in the array because the indexes change. Let me show you what I mean:

var elements = [1, 5, 5, 3, 5, 2, 4];
for(var i = 0; i < elements.length; i++){
if(elements[i] == 5){
elements.splice(i, 1);
}
}

The problem is that when elements[1] is removed, elements[2] becomes elements[1]. So first problem is that some elements are never examined. The other problem is that .length changes and if I hard code the bounds, then I might be trying to examine elements beyond the bounds of the array. So what's the best way to do this incredibly simple thing?

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最佳答案

Start from the top!

var elements = [1, 5, 5, 3, 5, 2, 4];
for(var i = elements.length - 1; i >= 0; i--){
if(elements[i] == 5){
elements.splice(i, 1);
}
}
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You could use the filter method here:

var elements = [1, 5, 5, 3, 5, 2, 4].filter(function(a){return a !== 5;});
//=> elements now [1,3,2,4]

Or if you don't want to touch elements:

var elementsfiltered
,elements = [1, 5, 5, 3, 5, 2, 4]
.filter( function(a){if (a!==5) this.push(a); return true;},
elementsfiltered = [] );
//=> elementsfiltered = [1,3,2,4], elements = [1, 5, 5, 3, 5, 2, 4]

See MDN documentation for filter

Alternatively you can extend the Array.prototype

Array.prototype.remove = Array.prototype.remove || function(val){
var i = this.length;
while(i--){
if (this[i] === val){
this.splice(i,1);
}
}
};
var elements = [1, 5, 5, 3, 5, 2, 4];
elements.remove(5);
//=> elements now [1,3,2,4]
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This is an example of using Array.indexOf, while and Array.splice to remove elements inline.

var elements = [1, 5, 5, 3, 5, 2, 4];
var remove = 5;
var index = elements.indexOf(remove);


while (index !== -1) {
elements.splice(index, 1);
index = elements.indexOf(remove);
}


console.log(elements);

On jsfiddle

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Using Array.shift():

var array = [1, 2, 3, 'a', 'b', 'c'];
while (array.length > 0) {
console.log(array.shift());
}

Edit: Probably does not suit the specs. I misread the question (only remove certain elements) and was too eager instead to add a method that was not mentioned yet...

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You could simply decrement i whenever you remove an item.

var elements = [1, 5, 5, 3, 5, 2, 4];


var l = elements.length;
for(var i = 0; i < l; i++){
if(elements[i] == 5){
elements.splice(i, 1);
i--;
}
}


console.log(elements);

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var elements = [1, 5, 5, 3, 5, 2, 4];
var i = elements.length;
while (i--) {
if (elements[i] == 5) {
elements.splice(i, 1);
}
}
console.log(elements);


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