javascript - Remove items from array with splice in for loop

Question

This question already has answers here:

Answer 1

Solution 1

You can loop backwards, with something like the following:

var searchInput, i;

searchInput = ["this", "is", "a", "test"];
i = searchInput.length;
while (i--) {
    if (searchInput[i].length < 4) {
        searchInput.splice(i, 1);
    }
}

DEMO: http://jsfiddle.net/KXMeR/

This is because iterating incrementally through the array, when you splice it, the array is modified in place, so the items are "shifted" and you end up skipping the iteration of some. Looping backwards (with a while or even a for loop) fixes this because you're not looping in the direction you're splicing.

---

Solution 2

At the same time, it's usually faster to generate a new array instead of modifying one in place. Here's an example:

var searchInput, newSearchInput, i, j, cur;

searchInput = ["this", "is", "a", "test"];
newSearchInput = [];
for (i = 0, j = searchInput.length; i < j; i++) {
    cur = searchInput[i];
    if (cur.length > 3) {
        newSearchInput.push(cur);
    }
}

where newSearchInput will only contain valid length items, and you still have the original items in searchInput.

DEMO: http://jsfiddle.net/RYAx2/

---

Solution 3

In addition to the second solution above, a similar, newer Array.prototype method is available to handle that better: filter. Here's an example:

var searchInput, newSearchInput;

searchInput = ["this", "is", "a", "test"];
newSearchInput = searchInput.filter(function (value, index, array) {
    return (value.length > 3);
});

DEMO: http://jsfiddle.net/qky7D/

---

References:

• Array.prototype.filter - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter
• Array.prototype.filter browser support - http://kangax.github.io/es5-compat-table/#Array.prototype.filter