This is not a huge problem as if you are outputting the floating point number, you would probably want to round it anyways. The biggest 'gotcha' is when doing equality comparisons between these numbers.

Consider the following:

    .1 + .2 == .3 // false

The way to 'get around' this is to have a value (usually called an epsilon) that is relative in magnitude to the numbers being compared. In this example, a value like .00001 as epsilon should work fine.

Anyways, all you have to do is check if the absolute difference of the numbers is less than the epsilon:

    var a = .1 + .2, b = .3, epsilon = .00001;
    console.log(Math.abs(a-b)<epsilon); // true

In short, try to not put yourself in a situation where you have to compare equality with doubles.

Floating point numbers in any language are inaccurate, if you're performing say, financial calculations then you can use fixed point numbers by using scaled integers. For example:

    var SCALE = 100; // 0.01
    
    var a = 0+1 * SCALE;  // e.g. 2.5 would be 2+5 * SCALE
    var b = 0+2 * SCALE;
    
    if (a + b == 0+3 * SCALE) {
      // this will work...
    }

    console.log(a / SCALE);

Is not a JS only thing, investigate how floating point values work.

See if there is a fixed precision arithmetic library for JS? (similar to BigDecimal in Java / Groovy)

Homework: 1) Google for such; 2) see which one doesn't suck.