#consolelog

jsを利用時にスマホで確認しててスマホのときに正確に値が切り替わってるのかわからない時ってないですか。私はあります。

結構スマホ時の挙動とかでこれ変わってる？ってのがちょこちょこでてくるのですが、その時にこちらは便利。ログがスマホでも出るのでほんとに変わってる？ってなることがなくて正確性が上がります。

How to stop using console.log() and start using your browser’s debugger

When I started my journey to become a software developer, I definitely ran into my fair share of bumps in the road. One of the most common struggles that most new developers face is debugging. At first, I thought I discovered the holy grail when I realized that I could open the console in chrome and console.log() out my values to discover where my bugs were. This turned out to be highly…

Console.log has become my best friend. That’s too much. It’s not like console.log will ever encourage me to go for that second scoop of ice cream. Rather, console.log has become my code-specific bestie, Connie Dotlogue. Looking back on how I started to learn JavaScript, console.log was not unlike knitting that gauge swatch. I hated it. It was a time waster. It came between coming up with a new…

Take the following code and run it in jsFiddle:

var Master = function (options) {     this.options = options;     console.log('>>OPTIONS');     console.log(options);     console.log('>>THIS.OPTIONS');     console.log(this.options);     console.log('>>THIS');     console.log(this); };

var Me = function () {};

Me.prototype = new Master({one: 234, two: 876});

var me = new Me();

me.options.one = 1;

If you inspect the output in the console, you'll see the following:

>>OPTIONS (index):23

Object {one: 234, two: 876} (index):24

>>THIS.OPTIONS (index):25

Object {one: 234, two: 876} (index):26

>>THIS (index):27

Master {options: Object}

options: Object

one: 1

two: 876

__proto__: Object

__proto__: Object

 If you expand "Master" (this), then expand options, you'll see that "options.one" is "1". Wait, why is "this.options.one" still "234"? For some reason, when you expand an object in the console, it shows you the updated referenced value. Remember that arrays and objects are passed by reference and not value. If console logging "this" shows the updated value, why doesn't plain old "this.options" get updated?

If you were to change the console.log(this) to alert(JSON.stringify(this)), you'll see that "this.options.one" is still "234". This is because the output hasn't reached "me.options.one = 1".