Javascript javascript子字符串
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javascript substring
提问by akula1001
the most darndest thing! the following code prints out 'llo' instead of the expected 'wo'. i get such surprising results for a few other numbers. what am i missing here?
最可恶的事情！以下代码打印出“llo”而不是预期的“wo”。对于其他一些数字，我得到了如此惊人的结果。我在这里错过了什么？
alert('helloworld'.substring(5, 2));
回答by Christoph
You're confusing substring()and substr(): substring()expects two indices and not offset and length. In your case, the indices are 5 and 2, ie characters 2..4 will be returned as the higher index is excluded.
你很困惑substring()并且substr():substring()需要两个索引而不是偏移量和长度。在您的情况下，索引是 5 和 2，即字符 2..4 将被返回，因为更高的索引被排除在外。
回答by Chirag
You have three options in Javascript:
在 Javascript 中有三个选项：
//slice
//syntax: string.slice(start [, stop])
"Good news, everyone!".slice(5,9); // extracts 'news'
//substring
//syntax: string.substring(start [, stop])
"Good news, everyone!".substring(5,9); // extracts 'news'
//substr
//syntax: string.substr(start [, length])
"Good news, everyone!".substr(5,4); // extracts 'news'
回答by Pekka
Check the substringsyntax:
检查substring语法：
substring(from, to)
fromRequired. The index where to start the extraction. First character is at index 0
toOptional. The index where to stop the extraction. If omitted, it extracts the rest of the string
子串（从，到）
从必需。开始提取的索引。第一个字符位于索引 0
到可选。停止提取的索引 。如果省略，则提取字符串的其余部分
I'll grant you it's a bit odd. Didn't know that myself.
我承认这有点奇怪。我自己不知道。
What you want to do is
你想做的是
alert('helloworld'.substring(5, 7));
回答by AutomatedTester
alert('helloworld'.substring(5, 2));
The code above is wrong because the first value is the start point to the end point.E.g move from char 5 which is oand go to char 2 which is the lso will get lloSo you have told it to go backwards.
上面的代码是错误的，因为第一个值是起点到终点。例如，从字符 5 移动o到字符 2，l这样就会得到llo所以你已经告诉它向后走。
What yuou want is
你想要的是
alert('helloworld'.substring(5, 7));
回答by Alexandru Diacov
See syntax below:
请参阅下面的语法：
str.substring(indexA, [indexB])
If indexA > indexB, the substring()function acts as if arguments were reversed.
如果indexA > indexB，substring()函数就像参数被反转一样。
Consider documentation here: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/substring
考虑这里的文档：https: //developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/substring
回答by Nayas Subramanian
This is What i have done,
这是我所做的，
var stringValue = 'Welcome to India';
// if you want take get 'India'
// stringValue.substring(startIndex, EndIndex)
stringValue.substring(11, 16); // O/p 'India'
