Question

I want to add multiple function onchange from javascript to the same input.
some thik like this:

this.el = document.getElementById(this.docID);

if(x==y)
{

 this.el.onchange += function(){ // some code }

}
if(a==b)
{

 this.el.onchange += function(){  // some code }

}

Answer 1

If you want to chain onchange functions, you can do something like this:

this.el = document.getElementById(this.docID);

if(x==y) {
  this.el.onchange = function(){ // some code }
}

if(a==b) {
  var oldOnChange = this.el.onchange;
  this.el.onchange = function(){ 
    // execute previous onchange function
    if(oldOnChange) oldOnChange();

    // some code 
  }
}

Like this you can also decide, whether you want the old onchange function to be executed before or after the new onchange code.