RegExp

1026.js

let permut = (arr) => {
    if (typeof arr === "string") {
        arr = arr.split("");
    }
    if (arr.length === 1) {
        return arr;
    }
    let rst = [];
    for (let i = 0, len = arr.length; i < len; i++) {
        let newArr = arr.slice();
        let ch = newArr.splice(i, 1)[0];
        permut(newArr).forEach(item => {
            rst.push("" + ch + item);
        });
        
    }
    return rst;
};

/* 给定的一个字符串（长度为 4），测试是否包含 "gimy"（位置不定）*/
let re1 = /([gimy])(?!\1)([gimy])(?!(?:\1|\2))([gimy])(?!(?:\1|\2|\3))([gimy])/;
let arr1 = permut("gimy");
for (let i = 0, len = arr1.length; i < len; i++) {
    console.assert(re1.test(arr1[i]))
}

/* 给定的一个字符串（长度不大于 4，可以为空），测试是否包含 "gimy"（位置不定）*/
let re2 = /^(?:([gimy]))?(?:(?!\1)([gimy]))?(?:(?!(?:\1|\2))([gimy]))?(?:(?!(?:\1|\2|\3))([gimy]))?$/;
let arr2 = permut("gimy");
for (let i = 0, len = arr2.length; i < len; i++) {
    console.assert(re2.test(arr2[i]))
}
console.assert(re2.test(""));
console.assert(re2.test("ig"));