Commonly used array string methods

function unique(arr){    var obj = {}    var data = []    for(var i in arr){        if(!obj[arr[i]]){
            obj[arr[i]] = true;
            data.push(arr[i]);
        }
    }    return data;
}

function getMaxProfit(arr){    var min = arr[0], max = arr[0];    for(var i=0;i<arr.length;i++){        if(arr[i]<min)
            min = arr[i];        if(arr[i]>max)
            max = arr[i];
    }    return max - min;
}

function randomString(n){    var str = &#39;abcdefghijklmnopqrstuvwxyz0123456789&#39;;    var tmp = &#39;&#39;;    for(var i=0;i<n;i++)
        tmp += str.charAt(Math.round(Math.random()*str.length));    return tmp;
}

function findMaxDuplicateChar(str) {    if(str.length == 1) {        return str;
    }    var charObj = {};    for(var i = 0; i < str.length; i++) {        if(!charObj[str.charAt(i)]) {
            charObj[str.charAt(i)] = 1;
        } else {
            charObj[str.charAt(i)] += 1;
        }
    }    var maxChar = &#39;&#39;,
        maxValue = 1;    for(var k in charObj) {        if(charObj[k] >= maxValue) {
            maxChar = k;
            maxValue = charObj[k];
        }
    }    return maxChar + &#39;：&#39; + maxValue;
}