Random JS notes

Js-Notes.js

//to convert string "true","false" to a boolean
var myBool = (mystring === "true");

//because using 
var myBool = eval(myString) // is evil ! bwahahah


//=================
//One of the weird behaviour and spec in Javascript is the typeof Array is Object.

//You can check if the variable is an array in couple of ways:

var isArr = data instanceof Array;
var isArr = Array.isArray(data);

//But the most reliable way is:
isArr = Object.prototype.toString.call(data) == '[object Array]';

//Also you can use jQuery isArray function:
var isArr = $.isArray(data);


//=================
//Check for array:

var arr = []; (or) arr = new Array();
var obj = {}; (or) arr = new Object();

arr.constructor.prototype.hasOwnProperty('push') //true

obj.constructor.prototype.hasOwnProperty('push') // false

//=================

//The difference you could see if you had another couple of functions:
var h = document.getElementById('a');
h.onclick = doThing_1;
h.onclick = doThing_2;

h.addEventListener('click', doThing_3);
h.addEventListener('click', doThing_4);

/* Functions 2, 3 and 4 work, but 1 does not. This is because addEventListener does not overwrite existing event handlers, whereas onclick overrides any existing onclick = fn event handlers.
The other significant difference, of course, is that onclick will always work, whereas addEventListener does not work in Internet Explorer before version 9. You can use the analogous attachEvent (which has slightly different syntax) in IE <9.
*/

//=================
btnSubmit.onclick = MyFunction(); //<== this is WRONG ! you are calling it
btnSubmit.onclick = MyFunction; //<== CORRECT WAY: assign function, not call it

function MyFunction() {
    this.disabled = true;
    //do other stuff
}
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