在Perl中,我可以使用以下语法多次重复一个字符:
$a = "a" x 10; // results in "aaaaaaaaaa"
有没有一种简单的方法在Javascript中实现这一点?我显然可以使用一个函数,但我想知道是否有内置的方法,或者其他一些巧妙的技术。
在Perl中,我可以使用以下语法多次重复一个字符:
$a = "a" x 10; // results in "aaaaaaaaaa"
有没有一种简单的方法在Javascript中实现这一点?我显然可以使用一个函数,但我想知道是否有内置的方法,或者其他一些巧妙的技术。
当前回答
String.prototype.repeat = function (n) { n = Math.abs(n) || 1; return Array(n + 1).join(this || ''); };
// console.log("0".repeat(3) , "0".repeat(-3))
// return: "000" "000"
其他回答
Lodash提供了与Javascript repeat()函数类似的功能,这在所有浏览器中都不可用。它名为_.repeat,从3.0.0版开始提供:
_.repeat('a', 10);
/**
* Repeat a string `n`-times (recursive)
* @param {String} s - The string you want to repeat.
* @param {Number} n - The times to repeat the string.
* @param {String} d - A delimiter between each string.
*/
var repeat = function (s, n, d) {
return --n ? s + (d || "") + repeat(s, n, d) : "" + s;
};
var foo = "foo";
console.log(
"%s\n%s\n%s\n%s",
repeat(foo), // "foo"
repeat(foo, 2), // "foofoo"
repeat(foo, "2"), // "foofoo"
repeat(foo, 2, "-") // "foo-foo"
);
截至目前,96.39%的浏览器支持String.repeat()。
function pad(text, maxLength){
return text + "0".repeat(maxLength - text.length);
}
console.log(pad('text', 7)); //text000
另一种选择是:
for(var word = ''; word.length < 10; word += 'a'){}
如果需要重复多个字符,请乘以条件:
for(var word = ''; word.length < 10 * 3; word += 'foo'){}
注意:您不必像word=Array(11)那样超出1。join('a')
最有效的方法是https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
下面是简短版本。
String.prototype.repeat = function(count) {
if (count < 1) return '';
var result = '', pattern = this.valueOf();
while (count > 1) {
if (count & 1) result += pattern;
count >>>= 1, pattern += pattern;
}
return result + pattern;
};
var a = "a";
console.debug(a.repeat(10));
Mozilla的Polyfill:
if (!String.prototype.repeat) {
String.prototype.repeat = function(count) {
'use strict';
if (this == null) {
throw new TypeError('can\'t convert ' + this + ' to object');
}
var str = '' + this;
count = +count;
if (count != count) {
count = 0;
}
if (count < 0) {
throw new RangeError('repeat count must be non-negative');
}
if (count == Infinity) {
throw new RangeError('repeat count must be less than infinity');
}
count = Math.floor(count);
if (str.length == 0 || count == 0) {
return '';
}
// Ensuring count is a 31-bit integer allows us to heavily optimize the
// main part. But anyway, most current (August 2014) browsers can't handle
// strings 1 << 28 chars or longer, so:
if (str.length * count >= 1 << 28) {
throw new RangeError('repeat count must not overflow maximum string size');
}
var rpt = '';
for (;;) {
if ((count & 1) == 1) {
rpt += str;
}
count >>>= 1;
if (count == 0) {
break;
}
str += str;
}
// Could we try:
// return Array(count + 1).join(this);
return rpt;
}
}