Why window.addEventListener does not work? [duplicate]

Question

On the window.onload event, I would like a function to be called. If I define it as given below, the function does not get called.

try {
    window.addEventListener("load", initialiseTable, false);
} catch(e) {
    window.onload = initialiseTable;
}

var initialiseTable = function () {
    console.log("hello world!!");
};

but if I change the function declaration to

function initialiseTable() {
    console.log("hello world!!");};

it works, any idea?

Answer 1

While you using var x = function(){} to declare functions, it should be declare before you call the function.

By function x (){}, x will exist in current scope, no matter how later it declare. Because such side effect, the var x = function(){} are more recommended. For example:

var user = 'alien';
if( user == 'alien') {
    function salute () { console.log("Welcome to Earth!"); }
} else {
    function salute (){ console.log("Good day!"); }
}

The salute() will print Good day! anyway, even though it not we want at all.

Answer 2

Declare the function before.

var initialiseTable = function () {
    console.log("hello world!!");
};
try {
    window.addEventListener("load", initialiseTable, false);
} catch(e) {
    window.onload = initialiseTable;
}

For more information about declaring a function read this: var functionName = function() {} vs function functionName() {}

Answer 3

Just put the function initialiseTable to the first position, eg:

var initialiseTable = function (){ /*[...]*/ }

After continue calling.