Node逻辑项目－自定义函数

需求：不使用官方内置函数，
使用node.js手动实现该函数功能：
1.字符串长度
2.截取字符串
3.字符串搜索
4.通过指定字符合并数组为字符串
5.分割字符串

   "use strict";

//1.字符串长度
function length(str) {
    var i = 0;
    var count = 0;
    for (i in str) {
        count++;
    }
    return count;
}

//2.截取字符串
function substr(str, start, len) {
    var res = "";
    if (start < 0 || len <= 0 || length(str) < start || length(str) < len || length(str) < parseInt(start) + parseInt(len)) {
        return false;
    } else {
        for (var i = 0; i < len; i++) {
            res += str[parseInt(start) + parseInt(i)];
        }
    }
    return res;
}

//3.字符串搜索
function find(s, str) {
    var i;
    if (1 === length(s)) {
        for (i in str) {
            if (s === str[i]) {
                return i;
            } else if (s !== str[i] && length(str) - 1 === i) {
                return -1;
            }
        }
    }
    if (length(s) > 1) {
        for (i in str) {
            // console.log(i);
            // console.log(s[0], str[i]);
            // console.log(s, substr(str, i, length(s)));
            // console.log("---");
            if (s[0] === str[i] && s === substr(str, i, length(s))) {
                return i;
            } else if (length(s) - 1 === i && s[0] !== str[i] && s !== substr(str, i, length(s))) {
                return -1;
            } else if (i == length(str) - 1) {
                // console.log(i);
                return -1
            }
        }
    }
}

//4.通过指定字符合并数组为字符串
function join(str, arr) {
    var tmp = [];
    var res = "";
    var result = "";
    for (var i in arr) {
        res += str + arr[i];
    }
    for (var j in res) {
        tmp[j] = res[j];
    }
    for (var k = 0; k < length(str); k++) {
        tmp[k] = "";
    }
    for (var z in tmp) {
        result += tmp[z];
    }
    return result;
}

//5.分割字符串
function split(s, str) {
    var strarr = [];    //字符串转数组
    var indexarr = [];  //结果组成的数组
    var resarr = [""];    //结果数组
    var index = 0;      //字符索引
    var kindex = 0;     //结果数组的索引
    var resultarr = []; //多个关键字的结果数组
    var result_k = 0;   //多个关键字的结果数组的索引
    if (1 === length(s)) {
        for (var i in str) {
            strarr[i] = str[i];
        }
        for (var j in strarr) {
            if (s !== strarr[j]) {
                indexarr[index] = j;
                index++;
            }
        }
        for (var k = 0; k < length(indexarr); k++) {
            if (parseInt(indexarr[k]) + 1 === parseInt(indexarr[k + 1])) {
                resarr[kindex] += strarr[parseInt(indexarr[k])];
            } else if (index === k + 1 && parseInt(indexarr[k]) - 1 !== parseInt(indexarr[k + 1])) {
                resarr[kindex] += strarr[parseInt(indexarr[k])];
            } else if (parseInt(indexarr[k]) + 1 !== parseInt(indexarr[k + 1])) {
                resarr[kindex] += strarr[parseInt(indexarr[k])];
                kindex++;
                resarr[kindex] = "";
            } else {
                kindex++;
                resarr[kindex] = "";
            }
        }
        return resarr;
    }
    if (length(s) > 1) {
        for (var i in str) {
            strarr[i] = str[i];
        }
        for (var j in strarr) {
            if (s[0] === strarr[j] && s === substr(str, j, length(s))) {
                var num = 0;
                for (index; num < length(s); index++, num++) {
                    indexarr[index] = j++;
                }
                num = 0;
            }
        }
        index = 0;
        var p = 0;
        for (p in strarr) {
            if (p != indexarr[index]) {
                resarr[kindex] += strarr[p];
            } else {
                index++;
                kindex++;
                resarr[kindex] = "";
            }
        }

        for (var u in resarr) {
            if ("" !== resarr[u]) {
                resultarr[result_k] = resarr[u];
                result_k++;
            }
        }
        return resultarr;
    }
}

module.exports = {length, substr, find, join, split};

好吧，我晕了…