leohxj
5/29/2014 - 7:04 AM

## 反转字符串, 效率的话iterative ,hack ,m5较高。测试地址为：http://jsperf.com/string-reverse-compare/5

``````// iterative

function string_reverse_1(str) {
var new_str = "";
for (var i = str.length - 1; i >= 0; i--) {
new_str += str.charAt(i);
}
return new_str;
}

// Hack
function string_reverse_1_hack(str) {
var new_str = "";
for (var i = str.length - 1; i >= 0; i--) {
new_str += str[i];
}
return new_str;
}

// iterative (m5)
function string_reverse_1b(str) {
var s = str,
new_str = "";
for (var i = s.length; --i >= 0; new_str += s[i]);
return new_str;
}

// iterative swapping
function string_reverse_2(str) {
if (str.length < 1) return "";

str = str.split(""); // make the string an array!
var tmp, len = str.length,
half_index = Math.floor(len / 2) - 1;;
for (var i = 0; i <= half_index; i++) {
tmp = str[len - i - 1];
str[len - i - 1] = str[i];
str[i] = tmp;
}

return str.join(""); // make the array a string again
}

// built-ins
function string_reverse_3(str) {
return str.split("").reverse().join("");
}

// recursive: reverse(str.substr(1)) + str[0]
function string_reverse_4(str) {
if (str.length < 2) return str;
return string_reverse_4(str.substr(1)) + str.charAt(0);
}

// recursive: reverse(str.last_half()) + reverse(str.first_half())
function string_reverse_5(str) {
if (str.length < 2) return str;

var half_index = Math.ceil(str.length / 2);
return string_reverse_5(str.substr(half_index)) + string_reverse_5(str.substr(0, half_index));
}
``````