In recent interview, interviewer has asked can you write polyfill for push() method in javascript.
any one know how to do this .?
Add a comment
|
2 Answers
push() adds one or more elements at the end of array and returns new length of array. You can use array's length property to add element at the end of it.
if (!Array.prototype.push) {
// Check if not already supported, then only add. No need to check this when you want to Override the method
// Add method to prototype of array, so that can be directly called on array
Array.prototype.push = function() {
// Use loop for multiple/any no. of elements
for (var i = 0; i < arguments.length; i++) {
this[this.length] = arguments[i];
}
// Return new length of the array
return this.length;
};
}
3 Comments
1983
You also need to update
this.length to make Array.prototype.push generic. So somewhere add this.length = Number(this.length) || 0; and this.length += 1.
Tushar
@KingMob I don't think that is needed. As if you have empty array, it's length will be always zero, no need to set this. And
this.length += 1 is not needed, as you're adding new elements in array, length will be automatically incremented by one, for each addition1983
I mean for
Array.prototype.push.call on, e.g. {length: 0}.if (!Array.prototype.push) {
Array.prototype.push = function () {
for (var i = 0, len = arguments.length; i < len; i++) {
this[this.length] = arguments[i];
if (Object.prototype.toString.call(this).slice(8, -1).toLowerCase() === 'object') {
this.length += 1;
}
}
return this.length;
};
}
1 Comment
dlondero
Maybe you could add some explanation so the OP can understand better?