#this #call #bind #apply

thisCallBIndApply.js

var obj = { name: 'smith' };

function outer() {
    (function inner() {
        console.log(this.name);
    }).call(this);
}

function outer() { // same result as above
    (function inner() {
        console.log(this.name);
    }.bind(this))();
}

outer.apply(obj);

function another() {
    function inna() {
        console.log(this.lag); // we don't know yet which value `this` will represent unless 
        //the act of invocation inna function happens. 
        
    }
    inna.call(this); // what value `this` gets in parenthesis has determined 
    // by a manner in which another function was called.
    
    // only after we have figured out the value of `this` in parenthesis, we
    // use it in executing code of our inna function. 
}

another.call(obj); // since we're using .call method and putting obj as argument, 
// 'this' in parenthesis will apply it as its value and never changes in duration 
// of a function run.