Variables

이 글은 자바스크립트의 Variables(변수)에 관한 개념 및 문법을 정리하기 위해 작성하였습니다.

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< Variables >

You can think of variables as little containers for information that live in a computer's memory.

Provide a way of labeling data with descriptive name.

 

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< Create a Variable >

let myName = LSH    //    myName variable is initialized with LSH
var myName = LSH
const myName = LSH

 

1. variable's name(camel casing) : myName

2. value : LSH

3. assignment operator(=)

 

• let(var) : can be reassigned,
                 can declare without a value  =>  in such a case, automatically initialized with undefined
• const : can't be reassigned,
              should have a value.
  

 

< Rules for naming variables >
1. cannot start with number
2. cannot be same as keywords
3. myname !== myName

 

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< Mathematical Assignment Operators >

• x += 1   //   x = x + 1
• x -= 1   //    x = x - 1
• x *= 1   //   x = x * 1
• x /= 1   //   x = x / 1
• increment operator(++)   //   +1
• decrement operator(--)   //   -1

 

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< String Concatenation with Variables >

ex)

let myPet = 'lion';
console.log('I own a pet ' + myPet + '.');
// I own a pet lion.

 

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< Template literals >

For Redability of code

 

•  `__________${ string }__________`

 

ex)

let myPet = 'lion';
console.log(`I own a pet ${myPet}.`);
// I own a pet lion.

 

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< typeof operator >

To check the data type

 

ex)

let unknown1 = 'foo';
console.log(typeof unknown1);   //   string

let unknown2 = 10;
console.log(typeof unknown2);   //   number

let unknown3 = true;
console.log(typeof unknown3);   //   boolean