在javascript中使用打字稿值

Question

hi i need to create a simple calcuator in angular with javascript .

now i use this code in javascript :

$(document).ready(function () {
  switch (this.operator) {
    case '+':
      this.ResultAns += this.first + this.second;
      break;
    case '-':
      this.ResultAns += this.first - this.second;
      break;
    case '*':
      this.ResultAns += this.first * this.second;
      break;
    case '/':
      this.ResultAns += this.first / this.second;
      break;
  }

and i defined this variable n type script:

  first: string = "";
  second: string = "";
  operator: string = "";
  ResultAns: number;

now when i need to use this variable it show undefined .

how can i use this variable in javascript ???????

Answer 1

this in JavaScript has different scopes. You could read a blog post, I googled one for you .
When you use a function keyword, this will refer to the caller (in your case, to document ).

You can use an arrow function :

$(document).ready(() => {
  switch (this.operator) {
    case '+':
      this.ResultAns += this.first + this.second;
      break;
    case '-':
      this.ResultAns += this.first - this.second;
      break;
    case '*':
      this.ResultAns += this.first * this.second;
      break;
    case '/':
      this.ResultAns += this.first / this.second;
      break;
  }

Anyway, in Angular, you shouldn't manipulate real DOM in your components. Hence, the use of jQuery is highly debatable, in most cases you should avoid it.