toFixed method without rounding to five digit

Question

I have a number var x = 2.305185185185195;

x = x.toFixed(5);

x = 2.30519 but I require this without rounding i.e. 2.30518

I read some thread with two decimal places but could not find for five decimal places.

Any help would be appreciated.

Answer 1

You can use an apropriate factor and floor it and return the result of the division.

Basically this solution moves the point to the left with a factor of 10^d and gets an integer of that and divided the value with the former factor to get the right digits.

function getFlooredFixed(v, d) {
    return (Math.floor(v * Math.pow(10, d)) / Math.pow(10, d)).toFixed(d);
}

var x = 2.305185185185195;

document.write(getFlooredFixed(x, 5));

Answer 2

If you need only a "part" of a number with a floating point without rounding, you can just "cut" it:

function cutNumber(number, digitsAfterDot) {
    const str = `${number}`;

    return str.slice(0, str.indexOf('.') + digitsAfterDot + 1);
}

const x = 2.305185185185195;

console.log(cutNumber(x, 5)); // 2.30518

This method is fast (https://jsfiddle.net/93m8akzo/1/) and its execution time doesn't depend on number or digitsAfterDot values.

You can also "play around" with both functions in a given fiddle for a better understanding of what they do.

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You can read more about slice() method here - MDN documentation

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NOTE This function is only an example, don't use it in production applications. You should definitely add input values validation and errors handling!

Answer 3

The Math.trunc() function returns the integer part of a number by removing any fractional digits

So you can multiply the number by 10^n where n is the desired number of precision, truncate the decimal part using Math.trunc(), divide by the same number (10^n) and apply toFixed() to format it (in order to get the form of 2.30 instead of 2.3 for example)

var x = 2.305185185185195;

console.log((Math.trunc(x*100000)/100000).toFixed(5));

Answer 4

I have sorted it out by adding a small amount if the decimal is 5, then rounding as usual:

function(value, decimals) {

    var decimals = decimals || 2;

    if( isNaN(value) ){ return 0; }
        
    var decimalPart = value.toString().trim().split('.').pop(),
        extra       = decimalPart.substr(decimals, decimalPart.length - decimals);

    if( extra == '5' && 
        decimalPart.length > decimals
    ){
        value = parseFloat(value) + (1 / ( Math.pow(10, decimals + 5) ) );  
    }

    return Number( parseFloat( value ).toFixed( decimals ) );
        
}