exponentialNumberOutputInJavascript.js

var value = '4200000000000000000000' // => '4200000000000000000000'
var float = parseFloat(value) // => 4.2e+21

return String(float) === String(value)
// => false
// => String(float) => String(4.2e+21) => '4.2e+21'
// => String(value) => String('4200000000000000000000') => '4200000000000000000000'