This question already has answers here:
How do I check if an array includes a value in JavaScript?
(60 answers)
Check if an element is present in an array [duplicate]
(9 answers)
Closed 4 years ago.
I recently starting learning JS so a beginner level answer would be great! Thanks.
function contains(arr, item) {
// check to see if item is inside of arr
// return true if it is, otherwise return false
}
What about something like this?
const arr = [1,2,3];
const el = 2;
console.log(arr.includes(el)) // true
Related
This question already has answers here:
What is destructuring assignment and its uses?
(3 answers)
What does this symbol mean in JavaScript?
(1 answer)
Javascript object bracket notation ({ Navigation } =) on left side of assign
(5 answers)
Closed 2 years ago.
I've recently came across this particular code:
const arr = [1,2,3];
const { length } = arr;
for (i = 0; i<=length; i++){
console.log(i)
}
Apparently this (const { length } = arr;) somehow works, but I haven't found any information on the Internet on either how or why should this actually work.
My question: how does this { } construction work and why doesn't it work when I change { length } to anything else, like { arrlength }? Can we possibly use this construction with other array's properties and how?
This question already has answers here:
Why do Array.prototype.slice.call(nodeList) for DOM elements?
(2 answers)
Explanation of [].slice.call in javascript?
(9 answers)
Closed 2 years ago.
In ES5 if have a NodeList and want to loop through it must first convert it to Array with slice and call. I can't understand correctly how this statement works. I need explanation.
let nodeList = document.querySelectorAll('div');
let nToArr = Array.prototype.slice.call(nodeList);
// Then Loop Through it ....
This question already has answers here:
How to observe value changes in JS variables
(3 answers)
Closed 5 years ago.
function getPercCalculated(x){
return (x*9.3)/100;
}
var x = 10;
var perx = getPercCalculated(x);
Instead of this I would like to call the getPercCalculated using dot operator like
var perx = x.getPercCalculated()
Can someone help me..!!
Number.prototype.getPercCalculated= function(){
return (this*9.3)/100;
};
This will attach the getPercCalculated to every number in your code tough
This question already has answers here:
Checking if an array has some items in coffeescript
(3 answers)
Closed 8 years ago.
I am trying to figure out if an array is empty. I tried this and it does not work.
a = []
if a == []
alert "empty"
I know I can check the length of the array but am curious why this does not work.
There is no direct empty check for arrays. You could do something like this though:
a = []
alert("empty") unless a.length
This question already has answers here:
How do I check if an array includes a value in JavaScript?
(60 answers)
Closed 10 years ago.
var a=new Array;
for (j=0;j<=10;j++) {
a[j]=Math.floor(Math.random()*99)+2
}
var check=Math.floor(Math.random()*99)+2
So how do I check whether check is a value of any of the a[j] (that is a[0] to a[10])? A good and simple method?
Try this:
a.indexOf(check) > -1