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javascriptclassprivate-members

What does the `#` symbol (number sign) do inside a JavaScript class?

I encountered code that contained the # sign. What is it used for? The code looks something like this:

class someObject{
  #someMethod(){
    //do something 
  }
}
Solution

  • It's a sigil (rather than an operator) that indicates that the member is private — in this case, a private method, but it's also used for private fields.

    You can't use a private method or private field in code outside the class declaring them. For instance:

    class Example {
    doSomething() {
        this.#method("from doSomething"); // <== Works
    }
    #method(str) {
        console.log("method called: " + str);
    }
}
const e = new Example();
e.doSomething();
e.#method(); // <=== FAILS