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Michael Merritt

I love all things Mobile and HTML5

Jan 20, 2015

What are some lesser known facts about JavaScript?

JavaScript is the language of the web and it has grown tremendously over the past few years . What are some interesting/lesser known facts about JavaScript?

#javascript

Responses(4)

Raja Sekar

Software Engineer | Javascript | Maths | Algorithms

Jan 25, 2016

I think the fact would be, many of the js developers have to understand the difference between having methods inside constructor and prototype.

function Person(name){
this.name = name;
this.sayname = function(){
    log(this.name)
}
}    

vs

Person.prototype.sayname = function(){
    log(this.name)
}

Will Cameron

JS, React, Node and all things web. http://camerow.github.io/

Feb 1, 2016

The difference here being that assigning to the prototype makes that function global for that prototype, whereas assignment in the constructor is unique to that instance? Or are you just referring to the fact you can assign methods in both the constructor fashion and as an attribute on the prototype? Just curious =)

Basically, if you have a method inside a constructor it will be available for all the instance of the object created, which will increase the memory space. If you have it in prototype It will be available for all the created object, but it is available for all the instance also. For example in the above code, if Person class is initiated fro 100 times, for each object sayname method will be available in the object itself. Assume it take 1kb, so finally 100kb will be utilized by the method if you have it inside constructor, but if u have it in prototype it will be present only once, it occupies only 1kb make your code cleaner and increse your performance also.

This is valid JS:

[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]][([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]+(!![]+[])[+[]]+(![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[!+[]+!+[]+[+[]]]+[+!+[]]+(!![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[!+[]+!+[]+[+[]]])()

:D Reference: Sweary website URL

Also:

0.1 + 0.2 === 0.3 // false

but

0.1 + 0.4 === 0.5 // true

Kent Brewster

Widgeteer, Pinterest

Feb 2, 2016

See Gary Bernhardt's "Wat," at destroyallsoftware.com/talks/wat, for far more interesting or lesser-known JS facts than you ever really wanted to know.

Timothy Jeng

Looking for the next "hello world"

Mar 19, 2018

Here's is an interesting one:

if (a == 0 && a == 1 && a == 2) {
  console.log(a); // ?
}

JavaScript implicitly calls valueOf method to convert an object into primitive value whenever it needs to (see mdn).

So if you design your object this way...

const a = {
  value: 0,
  valueOf() {
    return this.value++;
  }
}

You got yourself a self-increment object : )

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What are some lesser known facts about JavaScript?

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