How to access external function variables from inner functions in JavaScript?

Question

Am just getting the ropes of JS Fundamentals, bear with me.

Following is the code :

function FuncWithMathOps(x){
var x=x;

console.log("Value of x : "+x);

var SUM = function(x){
    var x=x;

    console.log("Value of x : "+x);
    console.log("Value of this.x : "+this.x);
}

var MUL = function(x){
    var x=x;

    console.log("Value of x : "+x);
    console.log("Value of this.x : "+this.x);
}

return {
    SUM:SUM,
    MUL:MUL
};

}

Both external function and inner functions variable names are same i.e., x & y. How do i access external function FuncWithMathOps variables from inner functions SUM & MUL ?

This does maybe sound stupid, but: Just don't name variables identically when you have to access them across scopes? — Sarah Groß
– Sarah Groß, Commented Feb 15, 2017 at 12:56
This may also be a duplicate of stackoverflow.com/questions/8453580/… — Sarah Groß
– Sarah Groß, Commented Feb 15, 2017 at 12:57
Possible duplicate of JavaScript: callback function parameter with same name as other variable? — evolutionxbox
– evolutionxbox, Commented Feb 15, 2017 at 13:06

Satpal · Accepted Answer · 2017-02-15 12:58:49Z

3

You can create a variable self which persist the reference to this, which can be used later.

function FuncWithMathOps(x) {
  this.x = x;
  var self = this;

  console.log("Value of x : " + x);
  var SUM = function(x) {
    console.log("Value of x : " + x);
    console.log("Value of this.x : " + self.x);
    return x + self.x;
  }

  return {
    SUM: SUM
  };
}

var fn = new FuncWithMathOps(10);
console.log(fn.SUM(5))

You can also use .bind()

function FuncWithMathOps(x) {
  this.x = x;
  console.log("Value of x : " + x);
  var SUM = function(x) {
    console.log("Value of x : " + x);
    console.log("Value of this.x : " + this.x);
    return x + this.x;
  }

  return {
    SUM: SUM.bind(this)
  };
}

var fn = new FuncWithMathOps(10);
console.log(fn.SUM(5))

answered Feb 15, 2017 at 12:58

Satpal

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