Question

94

In javascript, how to trigger event when a variable's value is changed?

rated 0 times [ 96] [ 2] / answers: 1 / hits: 69973 / 12 Years ago, thu, may 17, 2012, 12:00:00

I have two variables:

var trafficLightIsGreen = false; 

var someoneIsRunningTheLight = false;

I would like to trigger an event when the two variables agree with my conditions:

if(trafficLightIsGreen && !someoneIsRunningTheLight){

    go(); 

}

Assuming that those two booleans can change in any moment, how can I trigger my go() method when they change according to the my conditions?

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

yesseniadajab

Add To Favorites

Follow

Total Points: 258

Total Questions: 101

Total Answers: 127

Location: Mexico

Member since Mon, Sep 12, 2022

2 Years ago

answered 12 Years ago tristab · Accepted Answer

There is no event which is raised when a given value is changed in Javascript. What you can do is provide a set of functions that wrap the specific values and generate events when they are called to modify the values.

function Create(callback) {

  var isGreen = false;

  var isRunning = false;

  return { 

    getIsGreen   : function()  { return isGreen; },

    setIsGreen   : function(p) { isGreen = p; callback(isGreen, isRunning); },

    getIsRunning : function()  { return isRunning; },

    setIsRunning : function(p) { isRunning = p; callback(isGreen, isRunning); }

  };

}

Now you could call this function and link the callback to execute go():

var traffic = Create(function(isGreen, isRunning) {

  if (isGreen && !isRunning) {

    go();

  }

});



traffic.setIsGreen(true);