javascript - 在javascript中的某个位置找到单词

Question

对于'this is a sentence'的字符串输入，当position为6或7时，必须返回'is'。当position为0、1、2、3或4时，结果必须为'this'。

什么是最简单的方法？

Answer 1

function getWordAt (str, pos) {

    // Perform type conversions.
    str = String(str);
    pos = Number(pos) >>> 0;

    // Search for the word's beginning and end.
    var left = str.slice(0, pos + 1).search(/\S+$/),
        right = str.slice(pos).search(/\s/);

    // The last word in the string is a special case.
    if (right < 0) {
        return str.slice(left);
    }

    // Return the word, using the located bounds to extract it from the string.
    return str.slice(left, right + pos);

}

此函数接受任何空白字符作为单词分隔符，包括空格、制表符和换行符。本质上，它看起来:

• 为单词的开头，匹配/\S+$/
• 刚好超过单词的末尾，使用 /\s/

如所写，该函数将返回 ""如果给出了空白字符的索引；空格不是单词本身的一部分。如果您希望函数改为返回前面的单词，请更改 /\S+$/至 /\S+\s*/ .

---

这是 "This is a sentence." 的一些示例输出

0: This
1: This
2: This
3: This
4:
5: is
6: is
7:
8: a
9:
10: sentence.
// ...
18: sentence.

---

修改为返回前面的词，输出变为:

0: This
1: This
2: This
3: This
4: This
5: is
6: is
7: is
8: a
9: a
10: sentence.
// ...
18: sentence.