error in typescript for each loop syntax
angular, javascript, typescript
Solution
Your IDE is right. You are declaring `prop` with `let` and not with `const`.
`let` is for variables that are subject to change. For example:
let x = 5;
x = 7;
We declared `x` and then we changed it's value.
`const` is for values that won't change. For example:
const x = 5;
x = 7; // Throws an error.
So, in your case, as `prop` doesn't and won't change, has to be a constant (`const`):
for (const prop: string in c) {
...}
Check this documentation for a deeper understanding.
Problem
I'm trying to make a class with typescript 2.0.3 but I have some problems and I don't know why. this is my code ``` import { Component, OnInit } from '@angular/core'; import {Car} from '../interfaces/car'; class PrimeCar implements Car { constructor(public vin, public year, public brand, public color) {} } @Component({ selector: 'rb-test', templateUrl: './test.component.html', styleUrls: ['./test.component.css'] }) export class TestComponent implements OnInit { displayDialog: boolean; car: Car = new PrimeCar(null, null, null , null); selectedCar: Car; newCar: boolean; cars: Car[]; constructor() { } ngOnInit() { this.cars = [ {vin: '111', year: '5554' , brand: '5646' , color: '6466' }, {vin: '111', year: '5554' , brand: '5646' , color: '6466' }, {vin: '111', year: '5554' , brand: '5646' , color: '6466' }, {vin: '111', year: '5554' , brand: '5646' , color: '6466' } ]; } showDialogToAdd() { this.newCar = true; this.car = new PrimeCar(null, null, null, null); this.displayDialog = true; } save() { const cars = [...this.cars]; if (this.newCar) { cars.push(this.car); } else { cars[this.findSelectedCarIndex()] = this.car; } this.cars = cars; this.car = null; this.displayDialog = false; } delete() { const index = this.findSelectedCarIndex(); this.cars = this.cars.filter((val, i) => i !== index); this.car = null; this.displayDialog = false; } onRowSelect(event) { this.newCar = false; this.car = this.cloneCar(event.data); this.displayDialog = true; } cloneCar(c: Car): Car { const car = new PrimeCar(null, null, null, null); for (let prop: string in c) { car[prop] = c[prop]; } return car; } findSelectedCarIndex(): number { return this.cars.indexOf(this.selectedCar); } } ``` In the cloneCar method, I have this error when trying to write: ``` for (let prop: string in c) { ...} ``` Tslint: identifier 'prop' is never reassigned ,use const instead of let this is an image capture from my IDE: see error here NB: I'm using this code in angular project version 2.3.0 Some help, please!