Often in a JavaScript script, we iterate over some objects of a few built-in classes like Arrays, Dictionaries, Strings, Maps, etc. We iterate the objects using loops.
JavaScript supports different kinds of loops:
In this article, we will be learning about the difference between these two:
for (..in) loop
The JavaScript for (..in) statement loops through the enumerable properties of an object. The loop will iterate over all enumerable properties of the object itself and those the object inherits from its constructor’s prototype.
Syntax:
for (variable in object)
statement
Example: This example shows the use of a for-in loop.
let person = { firstName: "GeeksforGeeks" ,
lastName: "A Computer Science Portal for Geeks" ,
rank: 43
}; let userId = "" ;
let i; for (i in person) {
userId += person[i];
console.log(userId);
} |
GeeksforGeeks GeeksforGeeksA Computer Science Portal for Geeks GeeksforGeeksA Computer Science Portal for Geeks43
for (..of) loop
This for (..of) statement lets you loop over the data structures that are iterable such as Arrays, Strings, Maps, Node Lists, and more. It calls a custom iteration hook with instructions to execute on the value of each property of the object.
Syntax:
for (variable of iterable) {
statement
}
Example: This example shows the use of a for-of loop.
let text = [ "GeeksforGeeks" ,
" A Computer Science Portal for Geeks " ,
"43"
]; let userId = "" ;
let i; for (i of text) {
userId += i;
console.log(userId);
} |
GeeksforGeeks GeeksforGeeks A Computer Science Portal for Geeks GeeksforGeeks A Computer Science Portal for Geeks 43