求一串字符串中每個字符的出現次數

• for循環實現，最容易理解：

var arrString = 'fghffgaga';
var strArr = arrString.split('');
var rel = {
    };
var count = 1;
for (var i = 0; i < strArr.length; i++) {
    
    for (var j = i + 1; j < strArr.length; j++) {
    
        if (strArr[i] == strArr[j]) {
    
            count++;
            strArr.splice(j, 1);
            j = j - 1;              
        }

    }
    var qcount = count;
    count = 1;
    rel[strArr[i]] = qcount;    
}
console.log(rel); // {f: 3, g: 3, h: 1, a: 2}

• reduce() 方法實現

var arrString = 'fghffgaga';
var rel = arrString.split('').reduce(function(res, cur) {
    
res[cur] ? res[cur] ++ : res[cur] = 1
return res;
}, {
    })
console.log(rel); // {f: 3, g: 3, h: 1, a: 2}