docs: update padstart() and padend() (#8353)

* docs: update padstart() and padend() * Apply suggestions from code review Co-authored-by: A1lo <yin199909@aliyun.com>
mdn · Sep 7, 2022 · a6e2b31 · a6e2b31
1 parent e7fc8d2
commit a6e2b31
Show file tree

Hide file tree

Showing 2 changed files with 25 additions and 52 deletions.
diff --git a/files/zh-cn/web/javascript/reference/global_objects/string/padend/index.md b/files/zh-cn/web/javascript/reference/global_objects/string/padend/index.md
@@ -10,8 +10,9 @@ slug: Web/JavaScript/Reference/Global_Objects/String/padEnd
 
 ## 语法
 
-```plain
-str.padEnd(targetLength [, padString])
+```js
+padEnd(targetLength)
+padEnd(targetLength, padString)
 ```
 
 ### 参数
@@ -34,31 +35,6 @@ str.padEnd(targetLength [, padString])
 'abc'.padEnd(1);           // "abc"
 ```
 
-## Polyfill
-
-如果原生环境不支持该方法，在其他代码之前先运行下面的代码，将创建 `String.prototype.padEnd()` 方法。
-
-```js
-// https://github.com/uxitten/polyfill/blob/master/string.polyfill.js
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padEnd
-if (!String.prototype.padEnd) {
-    String.prototype.padEnd = function padEnd(targetLength,padString) {
-        targetLength = targetLength>>0; //floor if number or convert non-number to 0;
-        padString = String((typeof padString !== 'undefined' ? padString: ''));
-        if (this.length > targetLength) {
-            return String(this);
-        }
-        else {
-            targetLength = targetLength-this.length;
-            if (targetLength > padString.length) {
-                padString += padString.repeat(targetLength/padString.length); //append to original to ensure we are longer than needed
-            }
-            return String(this) + padString.slice(0,targetLength);
-        }
-    };
-}
-```
-
 ## 规范
 
 {{Specifications}}
@@ -67,6 +43,8 @@ if (!String.prototype.padEnd) {
 
 {{Compat}}
 
-## 另请参阅
+## 参见
 
+- [Polyfill of `String.prototype.padEnd` in `core-js`](https://github.com/zloirock/core-js#ecmascript-string-and-regexp)
 - {{jsxref("String.prototype.padStart()")}}
+- [A polyfill](https://github.com/behnammodi/polyfill/blob/master/string.polyfill.js)
diff --git a/files/zh-cn/web/javascript/reference/global_objects/string/padstart/index.md b/files/zh-cn/web/javascript/reference/global_objects/string/padstart/index.md
@@ -4,14 +4,15 @@ slug: Web/JavaScript/Reference/Global_Objects/String/padStart
 ---
 {{JSRef}}
 
-**`padStart()`** 方法用另一个字符串填充当前字符串 (如果需要的话，会重复多次)，以便产生的字符串达到给定的长度。从当前字符串的左侧开始填充。
+**`padStart()`** 方法用另一个字符串填充当前字符串（如果需要的话，会重复多次），以便产生的字符串达到给定的长度。从当前字符串的左侧开始填充。
 
 {{EmbedInteractiveExample("pages/js/string-padstart.html")}}
 
 ## 语法
 
-```plain
-str.padStart(targetLength [, padString])
+```js
+padStart(targetLength)
+padStart(targetLength, padString)
 ```
 
 ### 参数
@@ -27,6 +28,8 @@ str.padStart(targetLength [, padString])
 
 ## 示例
 
+### 简单示例
+
 ```js
 'abc'.padStart(10);         // "       abc"
 'abc'.padStart(10, "foo");  // "foofoofabc"
@@ -35,29 +38,18 @@ str.padStart(targetLength [, padString])
 'abc'.padStart(1);          // "abc"
 ```
 
-## Polyfill
-
-如果原生环境不支持该方法，在其他代码之前先运行下面的代码，将创建 `String.prototype.padStart()` 方法。
+### 将数字转换为固定长度的字符串
 
 ```js
-// https://github.com/uxitten/polyfill/blob/master/string.polyfill.js
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart
-if (!String.prototype.padStart) {
-    String.prototype.padStart = function padStart(targetLength,padString) {
-        targetLength = targetLength>>0; //floor if number or convert non-number to 0;
-        padString = String((typeof padString !== 'undefined' ? padString : ' '));
-        if (this.length > targetLength) {
-            return String(this);
-        }
-        else {
-            targetLength = targetLength-this.length;
-            if (targetLength > padString.length) {
-                padString += padString.repeat(targetLength/padString.length); //append to original to ensure we are longer than needed
-            }
-            return padString.slice(0,targetLength) + String(this);
-        }
-    };
+// JavaScript version of: (unsigned)
+//  printf "%0*d" width num
+function leftFillNum(num, targetLength) {
+  return num.toString().padStart(targetLength, 0);
 }
+
+const num = 123;
+console.log(leftFillNum(num, 5));
+// 预期输出: "00123"
 ```
 
 ## 规范
@@ -68,6 +60,9 @@ if (!String.prototype.padStart) {
 
 {{Compat}}
 
-## 另请参阅
+## 参见
 
+- [Polyfill of `String.prototype.padStart` in `core-js`](https://github.com/zloirock/core-js#ecmascript-string-and-regexp)
 - {{jsxref("String.prototype.padEnd()")}}
+- [A polyfill](https://github.com/behnammodi/polyfill/blob/master/string.polyfill.js)
+