constructor parameters in javascript

Question

I am trying to learn about constructors in JavaScript. I was watching some tutorial where this constructor:

    class Human{
        constructor() {
          this.gender = 'male'
         
        }
        printGender(){
          console.log(this.gender);
        }
      }

was also written with shorter syntax that looked like this:

    class Human{
        gender = 'male';
      
        printGender = () =>{
          console.log(this.gender);
        }
      }

I have no problem understanding this. However, what if I have some parameters. Like this for example:

    class Human{
        constructor(gender, height) {
          this.gender = gender;
          this.height = height;
    
        }
        printGender(){
          console.log(this.gender);
        }
      }

How do I write this shorter syntax and also have parameters? I could not find anything about this question. Any help?

Please avoid the term "ES7" in this context. ES7 came out in 2016 and does not include these features. These are just experimental proposals. — loganfsmyth
– loganfsmyth, Commented Apr 14, 2019 at 0:50
If whatever you were reading referred to this syntax as "ES7", you should probably stop reading it and find a different source. This is part of a TC39 proposal currently in progress. — Patrick Roberts
– Patrick Roberts, Commented Apr 14, 2019 at 1:02

Tobiq · Accepted Answer · 2019-04-14 00:46:38Z

3

The code you wrote would be acceptable.

You could additionally do:

class Human {
    gender;
    height;

    constructor(gender, height) {
      this.gender = gender;
      this.height = height;

    }
    printGender(){
      console.log(this.gender);
    }
  }

answered Apr 14, 2019 at 0:46

Tobiq

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2 Comments

Happy Coconut Over a year ago

Thanks, but my question is how can I do it without the constructor like second example, but with parameters.

Tobiq Over a year ago

You can't... That's the only way to your constructor's arguments. Unless, you have a super class that sets an argument to a property - i.e. within a React.Component you can use this.props within your subclass to set a property, because the super Component class assigned the props argument to the props property.

Raja Sekar · Accepted Answer · 2019-04-14 00:55:28Z

-1

Upfront field declarations is just a self documentation. To set the instance value we've to use constructor method during instantiation of the class like @Tobiq said.

answered Apr 14, 2019 at 0:55

Raja Sekar

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