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JavaScript JavaScript Objects Loop Through Objects Loop Through an Object's Properties

Posted by Thomas Ma
Thomas Ma
15,199 Points

Use a for...in loop to log each of the property names of the composer object to the console.

help

script.js 
const composer = {
  name: 'Edward Ellington',
  nickname: 'Duke',
  genres: ['jazz', 'swing'],
  instrument: 'piano'
};
Brandon White
.a{fill-rule:evenodd;}techdegree seal-36
Brandon White
Full Stack JavaScript Techdegree Graduate 34,660 Points

Hi Thomas Ma,

What is it specifically that you need help with?

Do you not understand the for...in syntax? If so, here’s a link to an article on how to use it.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in

2 Answers

Ryan Groom
Ryan Groom
18,674 Points
Ryan Groom
Ryan Groom
18,674 Points

Thomas Ma It is as simple as the following:

for (let property in composer) {
  console.log(property);
}

Where 'property' can be set to any name you see fit and 'composer' references the variable name of the object you created.

Brandon White
.a{fill-rule:evenodd;}techdegree seal-36
Brandon White
Full Stack JavaScript Techdegree Graduate 34,660 Points

You are correct, Ryan.

Although, you’ll generally want to declare the ‘property’ variable with either the let or const keyword. Otherwise, I’m pretty sure the variable gets defined on the global object (which is typically not what you’ll want).

So typically it’ll go for (let property in composer) {...} instead of for (property in composer) {...}.

Thomas Ma
Thomas Ma
15,199 Points

I need the answer

shahzaib rafiq
PLUS
shahzaib rafiq
Courses Plus Student 3,001 Points
shahzaib rafiq
shahzaib rafiq
Courses Plus Student 3,001 Points

Hello, If you want to print the property name or key like 'name' and 'nickname' of the object composer by using 'for in' loop the syntax is for ( var propertyName in composer ){ console.log(propertyName); } this just gives you access to the key name.

However, if you want to access the property value like 'Edward Ellington' and 'Duke' you use "square bracket notation" Like for ( var propertyName in composer ){ console.log(composer[propertyName]); } in fact, the only way to access an object property using the 'for in' loop is with the bracket notation.