JS_剑指 Offer 05. 替换空格

输入：s = "We are happy."
输出："We%20are%20happy."

思路：遍历一遍即可

/**
 * @param {string} s
 * @return {string}
 */
var replaceSpace = function(s) {
    let res = '';
    for(let i = 0; i < s.length; i ++){
        if(s[i] == ' '){
            res+='%20';
        }else{
            res+=s[i];
        }
    }

    return res;
};