Question

What is the most effective to map ranges using Arrays in JavaScript?

I have this:

var def = [70,200,1000];

And an array of possible numbers, say:

var n = [23,45,74,120,240,800,1204,2000];

Now, how can I extract the closest value from n that matches the values from def?

In the example above, I would get [74,240,800]. I hope I make myself clear…

Answer 1

http://jsfiddle.net/8bY2M/

var def = [70,200,1000];
var n = [23,45,74,120,240,800,1204,2000];

var result = [];

for (var i = 0; i < def.length; i++){
    var val = def[i];
    for (var j = 0; j < n.length; j++){
        var nVal = n[j];                
        if (nVal > val){
            var closest = n[j-1] == undefined ? nVal : 
                nVal - val > val - n[j-1] ? n[j-1] : nVal;

            result.push(closest);
            break;
        }    
    }
}

console.log(result); // outputs: [74, 240, 800] 

Note that this will go with the larger value in the event of two matches. (i.e. if you are trying to match 70, and n contains 66 and 74, this will match it with 74)