what does the symbol '$' mean in angular?

Question

What does mean by $ in ${some_var}

search(term:string) {
        let promise = new Promise((resolve, reject) => {
        let apiURL = `${this.apiRoot}?term=${term}&media=music&limit=20`;
        this.http.get(apiURL)
            .toPromise()
            .then(
            res => { // Success
                console.log(res.json());
                resolve();
                   }
                 );
        });
        return promise;
    }

Answer 1

Thats template literals to use for string interpolation.

Earlier we use below code for string concatenation

var user ="lokesh"

var testStr = "my name is "+ user 

Now in typescript and in ECMA6 that can be used like this

var user ="lokesh"

var testStr = `my name is ${user}`

In your case old version

 let apiURL = this.apiRoot + '?term='+term+'&media=music&limit=20';

typescript and ECMA6

 let apiURL = `${this.apiRoot}?term=${term}&media=music&limit=20`;

Answer 2

$ {}用作模板字符串https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals中的占位符

Answer 3

There are other usage of $ sign:

<li *ngFor="let hero of heroes$ | async" >

in this case, The $ is a convention that indicates heroes$ is an Observable, not an array.