How to expose only a function and not the variables from a class function?

Question

Suppose I have this code:

function GraphFactory() {

  this.nodeNames = [];
  this.pinnedNodes = [];


  this.initPinnedNodes = function(nodes) {
    if (nodes) {
      this.pinnedNodes = nodes;
    } else {
      this.pinnedNodes = [];
    }
  }
  this.checkIfPinned = function(node) {
    if (this.pinnedNodes.indexOf(node) > -1) {
      return true;
    } else {
      return false;
    }
  }
  this.addToPinnedNodes = function(name) {
    this.pinnedNodes.push(name);
    return true;
  }
  this.removeFromPinnedNodes = function(name) {
    this.pinnedNodes.splice(this.pinnedNodes.indexOf(name), 1);
    return true;
  }
}

let graphFactory = new GraphFactory();

Right now i can access both the function

graphFactory.checkIfPinned(label);

but also directly the variable

graphFactory.pinnedNodes

How would I set things up so only the functions, but not the variables could get accessed?

https://stackoverflow.com/questions/2636453/is-it-possible-to-create-a-hidden-property-in-javascript is this what you're looking for? — briosheje, Apr 12 '19 at 10:24

score 1 · Accepted Answer · answered Apr 12 '19 at 10:24

1

Use variables instead of properties on the object.

let nodeNames = [];

They'll be closed over by your dynamically assigned instance methods.

Or see this question for the modern approach.

answered Apr 12 '19 at 10:24

Quentin

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Use `let` when declaring the variable. – Quentin Apr 12 '19 at 10:25

score 0 · Answer 2 · answered Apr 12 '19 at 10:27

With the current construct, you can use a closure per object, practically a local variable in your constructor function:

function GraphFactory() {
  var nodeNames = [];
  var pinnedNodes = [];

  this.initPinnedNodes = function(nodes) {
    if (nodes) {
      pinnedNodes = nodes;
    } else {
      pinnedNodes = [];
    }
  }
  this.checkIfPinned = function(node) {
    if (pinnedNodes.indexOf(node) > -1) {
      return true;
    } else {
      return false;
    }
  }
  this.addToPinnedNodes = function(name) {
    pinnedNodes.push(name);
    return true;
  }
  this.removeFromPinnedNodes = function(name) {
    pinnedNodes.splice(this.pinnedNodes.indexOf(name), 1);
    return true;
  }
}

let graphFactory = new GraphFactory();

However such variables will not be accessible to methods you add later, from outside. For example that nodeNames exists in vain this way.

How to expose only a function and not the variables from a class function?

2 Answers2