Is there an easy way to make an array have a specific amount of element. In the sense that if you push more into it, it overides the first element.
for example i want an array to only contain 2 elements. if i push a third element, it should overwrite the earliest element (the first in). Like a stack.
You could use a counter and use the modulo with the wanted length for inserting.
function push(array, length) {
var counter = 0;
return function (value) {
array[counter % length] = value;
counter++;
};
}
var array = [],
pushToArray = push(array, 2);
pushToArray(1);
console.log(array);
pushToArray(2);
console.log(array);
pushToArray(3);
console.log(array);
pushToArray(4)
console.log(array);.as-console-wrapper { max-height: 100% !important; top: 0; }So as i have commented above you might do this by array sub-classing. The following snippet introduces a new Array structure with two new methods as last and push. However our new push shadows the real push method of the Array.prototype. The new push takes the first argument as the limit to the array length such as [1,2,3].push(4,"a","b","c") will limit the length to 4 and the result would be [3,"a","b","c"]. The return value will be the deleted elements in an array as we are using splice under the hood.
function SubArray(...a) {
Object.setPrototypeOf(a, SubArray.prototype);
return a;
}
SubArray.prototype = Object.create(Array.prototype);
SubArray.prototype.last = function() {
return this[this.length - 1];
};
SubArray.prototype.push = function(lim,...a){
Array.prototype.push.apply(this,a);
return this.splice(0,this.length-lim);
};
myArray = new SubArray(1,2,3);
myArray.last();
myArray.push(4,"a","b","c");
console.log(myArray);