CODEWITHSUNDEEP
javascript
WillD
WillD

Reputation: 6512

programmatically determining if value falls within a range, given N ranges

Suppose I have an array that looks like this:

const points = [ .1, .2, .25, .6, .72, .9 ]

Each of these values represents points/stops along a line. My goal is to have a function which returns the index of the range (the space between two adjacent array values) where an input value falls.

For example if I put in .3 my function would return 3 because .3 is between .25 and .6 and that is the 4th range, as defined by my array. Note that I consider -infinity to .1 the first (implicit) range.

So far I have come up with this:

function whichRange(input){
    if(input < points[0]) {
        return 0;
    }
    else if( input >= points[0] && input < points[1]){
        return 1;
    }
    else if( input >= points[1] && input < points[2]){
        return 2;
    }
    else if( input >= points[2] && input < points[3]){
        return 3;
    }
    else if( input >= points[3] && input < points[4]){
        return 4;
    }
    else if( input >= points[4] && input < points[5]){
        return 5;
    }
    else if (input >= points[5]) {
        return 6;
    }
}

However this supposes I will always have exactly 6 stops in my array.

What if my array has n stops. How can I construct a similar, but more general function?

Upvotes: 2

Views: 318

Answers (1)

Nina Scholz
Nina Scholz

Reputation: 386620

You could use Array#findIndex and check if the index is found or not, then return the length of the array.

function getIndex(array, value) {
    var index = array.findIndex(v => v >= value);
    return index !== -1
        ? index
        : array.length;
}

const points = [.1, .2, .25, .6, .72, .9];

console.log(getIndex(points, .3)); // 3
console.log(getIndex(points, .9)); // 5
console.log(getIndex(points, 1));  // 6

Upvotes: 5

Related Questions