CONDITIONAL(조건문)

Always need ‘Comparison Operator’(비교 연산자)

• > more than
• < less than
• >= ane more
• <= and less
• === equal
• !== not equal
• Result is always ‘boolean’(true/false)

• else can be omitted depends on function.

To apply 2 conditions together, use ‘Logical Operator’(논리 연산자)

AND: &&

OR: ||

NOT: ! (falsy) **memorize

Number.isNaN(anything)

• In order to check NaN
• reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean

STRING METHODS = IMMUTABLE

• If you do string type + any different type, it becomes string type automatically.

length,

find value,

• if there is no value, it returns -1

lastIndexOf

• find index from the back and check the order from the front.

str.includes(searchValue)

• does not work at outdated browser and returns as Boolean

separate,

get certain values from the string,

• if start value is negative, it applies as 0.
• To see difference: reference: https://stackoverflow.com/questions/2243824/what-is-the-difference-between-string-slice-and-string-substring

Uppercase/Lowercase

Math

• Math.floor(x) = 내림;
• Math.ceil(x) = 올림;
• Math.round(x) = 반올림;
• Math.pow(base, exponent) = 제곱

trim() : remove space inside string

\n : new line