Javascript Number toPrecision()

Introduction

The Javascript Number toPrecision() method format Number object to string by the specified precision. 

numObj.toPrecision([precision])
Parameter Optional Meaning
precision Optional An integer specifying the number of significant digits.

If the precision argument is omitted, it behaves as Number.prototype.toString().

If the precision argument is a non-integer value, it is rounded to the nearest integer.

The toPrecision() method returns either the fixed or the exponential representation of a number, depending on which makes the most sense.

This method takes one argument, which is the total number of digits to use to represent the number, not including exponents. 

let num = 99; /*from w  w w  . j  a  v a 2s .  com*/
console.log(num.toPrecision(1));  // "1e+2" 
console.log(num.toPrecision(2));  // "99" 
console.log(num.toPrecision(3));  // "99.0"

In this example, the first task is to represent the number 99 with a single digit, which results in "1e+2".

The toPrecision() method determines whether to call toFixed() or toExponential() based on the numeric value.

Using toPrecision() 

let numObj = 12345.123456

console.log(numObj.toPrecision());/*from  w ww . j av  a2 s .c  om*/
console.log(numObj.toPrecision(5));
console.log(numObj.toPrecision(2));
console.log(numObj.toPrecision(1));

numObj = 0.000123

console.log(numObj.toPrecision());
console.log(numObj.toPrecision(5));
console.log(numObj.toPrecision(2));
console.log(numObj.toPrecision(1));

console.log((1234.5).toPrecision(2))



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