This function removes duplicates from an array. It can also be used to remove duplicates that are near another value with a tolerance

removeDuplicates.js

var removeDuplicates = function(arr, condition) {
    var conditionType = typeof condition;
    
    if(conditionType !== 'function' || conditionType === 'undefined') {
        condition = function(a, b) {
            return a === b;
        };
    }
    
    var seen = [];
    
    while(arr.length) {
        var a = arr[0];
        //only one element left so we're done
        if(arr.length === 1) {
            seen.push(a);
            break;
        }
        var temp = [];
        seen.push(a); //we already scanned these
        for(var i=1; i<arr.length; i++) {
            var b = arr[i];
            //if the number is outside the specified tolerance
            if(!condition(a, b))
                temp.push(b);
        }
        //start over with the remainder
        arr = temp;
    }
    
    return seen;
};

// ===============================================================================================
// USAGE:
var arr = ['matt', 'tom', 'tina', 'matt'];
console.log(removeDuplicates(arr));

//Remove duplicates within a tolerance. The first value seen will be returned.
var arr2 = [0, 3.0001, 1.000001, 2, 2.1, 3, 1, 2.99999999999, 4, 2, 0, 3];
console.log(removeDuplicates(arr2, (a, b) => Math.abs(a-b) <= 0.001));

var isInt = function(n) {
    return n % 1 === 0;
};

//Move the integers to the front if you want them to be seen first
arr2 = arr2.sort(function(a, b) {
    var ret = 0;
    if( isInt(a) && isInt(b)) {
        ret = 3;
    }
    else if(isInt(a)) {
        ret = 2;
    }
    else if(isInt(b)) {
        ret = 1;
    }
    
    return ret;
});

console.log(removeDuplicates(arr2, (a, b) => Math.abs(a-b) <= 0.001));