The value produced by the interval in Angular is not being displayed in the browser using double curly braces

I am attempting to display the changing value on the web page every second, but for some reason {{}} is not functioning correctly. However, when I use console.log, it does show the changing value.

Here is an excerpt from my .ts code:

randomValue: number;
processIncrementValue(){    
this.randomValue = Math.floor((Math.random()*100)+1);
console.log("Generating random number: " + this.randomValue);
}
// This function changes the value upon button press
start(){
console.log("Generating random number: start " + this.randomValue);
this.myVar = setInterval(this.processIncrementValue, 1000);
}

Snippet from .HTML file:

<div class="row">
<button type="button" class="btn btn-primary" (click)="start()">Start</button>
<hr>
<div class="row">
<p>My name is: {{randomValue}}</p>
</div>
</div>

Answer №1

Utilize the ES6 arrow function to bind setInterval to scope

this.myVar = setInterval(()=>{this.processIncrementValue()}, 1000);

When using

setInterval(function () { doThing() });
, it associates this with the window object. Therefore, in the function doThing(), if you reference this.doSomething, your code will attempt to locate a variable within the window object named doSomething, which is non-existent.

By utilizing the arrow function, this is bound to the current scope, specifically your angular component.


Source: https://www.w3schools.com/js/js_arrow_function.asp

In traditional functions, the this keyword represented the entity that invoked the function, whether it was the window, document, a button, or another element.

However, with arrow functions, the this keyword consistently represents the entity that defined the arrow function.

Answer №2

If you're looking for a solution, consider implementing the following code in your .TS and .HTML files:

.TS file

randomValue: number; // = 0 if initialization is needed

processIncrementValue() {
    this.randomValue = Math.floor((Math.random() * 100) + 1);
    setTimeout(() => {
       this.processIncrementValue();
    }, 1000);
  }

.HTML file

<div class="row">
  <button type="button" class="btn btn-primary" (click)="processIncrementValue()">Start</button>
  <div class="row">
    <p>my name is: {{randomValue}}</p>
  </div>
</div>

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