This content originally appeared on DEV Community and was authored by Ramya K
for loop for-in loop for-of loop
for loop:
We need to provide initialization, condition and increment/decrement to iterate the elements one by one. It is used when the number of iteration is known.
let a=[10,100,1000];
for(let i=0;i<a.length;i++){
console.log(a[i]);
}
let str="Javascript";
for(let i=0;i<str.length;i++){
console.log(str[i]);
}
for-of:
We no need to provide initialization and condition and just follow the syntax to iterate all the elemnts from the array and string. It is used to iterate generator function values too.
//for-of loop
let b=[101,1001,10001];
for(let val of b){
console.log(val);
}
It is used to iterate generator function values too.
function* newgen(){
yield "one";
yield "two";
yield "three";
}
let val=newgen();
for(let gen of val){
console.log(gen);
}
To iterate for and for of values are to be in single values. In object values are in key-value pair so cant iterate using for-of to overcome that for-in loop is used.
for-in:
To iterate object values for-in loop is used. Array and string also we can iterate.
//for-in
// to iterate objects using for-in
let person={
pname:"AAA",
age:11,
sibling:["BB","CC"],
hobby(){
console.log("Watching movie");
},
pcolor:{
hair:"black",
eye:"blue"
}
}
for(let key in person ){
console.log(person[key]);
}
// to iterate array using for-in
let arr=["a",'b',"c"];
for(let key in arr){
console.log(arr[key]);
}
// to iterate string using for-in
let st="Hello";
for(let key in st){
console.log(st[key]);
}
This content originally appeared on DEV Community and was authored by Ramya K
Ramya K | Sciencx (2025-06-26T21:23:45+00:00) for vs for-in vs for-of loop in Javascript. Retrieved from https://www.scien.cx/2025/06/26/for-vs-for-in-vs-for-of-loop-in-javascript/
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