当一个字符串被传递给一个带有返回语句的函数时,你如何在JavaScript中反转它,而不使用内置函数(.reverse(), . charat()等)?
当前回答
真正的答案是:你不能把它颠倒过来,但是你可以创建一个颠倒过来的新字符串。
Just as an exercise to play with recursion: sometimes when you go to an interview, the interviewer may ask you how to do this using recursion, and I think the "preferred answer" might be "I would rather not do this in recursion as it can easily cause a stack overflow" (because it is O(n) rather than O(log n). If it is O(log n), it is quite difficult to get a stack overflow -- 4 billion items could be handled by a stack level of 32, as 2 ** 32 is 4294967296. But if it is O(n), then it can easily get a stack overflow.
有时候面试官还是会问你,“作为练习,你为什么不用递归来写呢?”就是这样:
String.prototype.reverse = function() {
if (this.length <= 1) return this;
else return this.slice(1).reverse() + this.slice(0,1);
}
测试运行:
var s = "";
for(var i = 0; i < 1000; i++) {
s += ("apple" + i);
}
console.log(s.reverse());
输出:
999elppa899elppa...2elppa1elppa0elppa
为了尝试获得堆栈溢出,我在谷歌Chrome中将1000更改为10000,它报告:
RangeError: Maximum call stack size exceeded
其他回答
String.prototype.reverse_string=function() {return this.split("").reverse().join("");}
or
String.prototype.reverse_string = function() {
var s = "";
var i = this.length;
while (i>0) {
s += this.substring(i-1,i);
i--;
}
return s;
}
保持干燥和简单,傻!!
function reverse(s){
let str = s;
var reverse = '';
for (var i=str.length;i>0;i--){
var newstr = str.substring(0,i)
reverse += newstr.substr(-1,1)
}
return reverse;
}
var str = 'sample string';
[].map.call(str, function(x) {
return x;
}).reverse().join('');
OR
var str = 'sample string';
console.log(str.split('').reverse().join(''));
//输出:“gnirts elpmas”
使用Array函数,
String.prototype.reverse = function(){
return [].reduceRight.call(this, function(last, secLast){return last + secLast});
}
function reverse(str){
var s = "";
for (var i = str.length - 1; i >= 0; i--){
s += str[i];
}
return s;
};
reverse("your string comes here")