var a1 = {}, b1 = '123', c1 = 123;
a1[b1] = 'b';
a1[c1] = 'c';
console.log(a1[b1]);

var a2 = {}, b2 = Symbol('123'), c2 = Symbol('123');
a2[b2] = 'b';
a2[c2] = 'c';
console.log(a2[b2]);

var a3 = {}, b3 = {key: '123'}, c3 = {key: '456'};
a3[b3] = 'b';
a3[c3] = 'c';
console.log(a3[b3]);


/**
result:
c, b, c

主要考点:
对象的 key 值只能为字符串、Symbol
*/

找出字符串数组中，每一项最大的公共前缀

• 1. 假设第一个元素为最大的公共前缀，
• 1. 然后与数组的下一个元素进行对比，得出最大的公共前缀，覆盖之前的最大的公共前缀
• 1. 重复第 2 步，一次对比到数组的最后一个元素

const arr = ['aaaf', 'aadc', 'ad', 'a', 'abf']

function longest(arr) {
    let result = ''

    function _transform(publicStr, str) {
        let result = ''

        for (let i = 0; i < publicStr.length; i++) {
            const currentStr = publicStr[i]

            if (currentStr === str[i]) {
                result += currentStr
            } else {
                break
            }
        }

        return result
    }

    for (let i = 0; i < arr.length; i++) {
        const currentStr = arr[i]

        if (currentStr === '') return ''

        if (i === 0) {
            result = currentStr
            continue
        }

        result = _transform(result, currentStr)
    }

    return result
}

console.log(longest(arr))