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StringToNumber.md

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Difference between ~~, + and parseInt and Number()

An empty string ("") evaluates to 0 by the unary plus operator and ~~ operator, while parseInt evaluates to NaN.

~~""          //Output -  0
+""           //Output - 0
parseInt("")  //Ooutput - NaN

parseInt builds and parses the string from left to right. While parsing if it gets an invalid or non-numnerical character it returns whatever has been parsed so far. On the contrary unary+ operator gives NaN and ~~ operator gives output as 0

~~"12rt"          //Output -  NaN
+"12rt"           //Output - NaN
parseInt("12rt")  //Ooutput - 12

link for complete difference

Conversion of undefined

~~null          //Output -  0
+null          //Output - 0
parseInt(null)  //Ooutput - NaN

Conversion of undefined

~~undefined          //Output -  0
+undefined          //Output - NaN
parseInt(undefined)  //Ooutput - NaN
typeof NaN //Number
123/0 //Infinity
var a = 123/0 
typeof a //Number

isNaN("2") //false - JS internally tries to convert this to number using parseInt("2").

Values that are truthy or falsey

Any number is except 0 are true undefined, NaN, null is false

Infinity is true

Strings with characters are true but empty string is false

Implicit typecasting

var myString = "88";
var myNum = 88

if(myNum == myString){
   console.log("mystring is equal to mynum");
}