Undefined

by obobruyko

JavaScript

// Accessing a declared but not yet initialized variable

var a;
console.log("a = " + a);
a = 5;

// Implicit returns of functions due to missing return statements
/*
function noReturn() {      
    // return 2;
};

console.log("noReturn() returns: " + noReturn());
*/
// Look-ups of non-existent properties
/*
function nonExistent() {
    var obj = {name: "name"};       
    
    console.log("obj.name = " + obj.name); 
    console.log("obj.value = " + obj.value);
    
    var arr = [];
    arr[0] = 1;
    
    console.log("arr[0] = " + arr[0]); 
    console.log("arr[1] = " + arr[1]);
};

nonExistent();
*/
// Function parameters that do not have any value passed
/*
function noPassedValue(param) {
    console.log("param = " + param);
}

noPassedValue();
*/