typescript destructuring object literal in construct of the class, default properties does not work

Question

I\'m trying to use default values for destructuring object literal, but I don\'t get the default values, just \'undefined\'. What is the right way?

import { Comp         


        

Answer 1

When you don't assign default value for object fields, typescript will treat it as a normal parameter(type of object) like below:

constructor(obj: any = {id:3, name: 'defaulthero'})

• when creating a new instance of hero by new Hero(), there will be no parameter for constructor, so the default {id:3, name: 'defaulthero'} will be used.

• when creating a new instance of hero by new Hero({}), there will be one parameter which is an object with no fields and it will be used as the income parameter and take the place of default {id:3, name: 'defaulthero'}.(the same as new Hero ( {id: 0} ))

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as you have one commented line at your code block, you can assign default value for fields of object parameters with the below changes:

constructor({id=3, name='defaulthero'}: {id?: number, name?: string } = {}) {
  this.id = id;
  this.name = name;
}

Plunker demo