check if value is nan javascript code example

Example 1: compare NaN in javascript if condititon

// Use isNaN() 
// In javascript compare NaN direct alweys return false
let num1 = Number("Vishal");

// This code never work
if(num1 == NaN){  // Direct compare NaN alweys return false so use isNaN() function
  ....... Your Code .......
}  

// This code work
if(isNaN(num1){
  .........Your Code .......
}

Example 2: javascript check if is nan

function isNaN(x) {
   return x !== x;
};
isNaN(NaN);//true

Example 3: check if value is NaN

Number.isNaN(123)

Example 4: check if var is NaN

let b=1
let n=readline()
if(isNaN(b)){
  console.log("You typed 0!")
}else{
  console.log("You did not type 0!")
}

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