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Detailed introduction to the summary of methods used by replace in javascript
Detailed introduction to the summary of methods used by replace in javascript
这篇文章主要为大家详细介绍了javascript中replace的使用方法，使用replace和正则表达式共同实现字符串trim方法，具有一定的参考价值，感兴趣的小伙伴们可以参考一下
ECMAScript提供了replace()方法。这个方法接收两个参数，第一个参数可以是一个RegExp对象或者一个字符串，第二个参数可以是一个字符串或者一个函数。现在我们来详细讲解可能出现的几种情况。
1. 两个参数都为字符串的情况
var text = 'cat, bat, sat, fat'; // 在字符串中找到at，并将at替换为ond，只替换一次 var result = text.replace('at', 'ond'); // "cond, bat, sat, fat" console.log(result);
2. 第一个参数为RegExp对象，第二个参数为字符串
我们可以发现上面这种情况只替换了第一个at，如果想要替换全部at，就必须使用RegExp对象。
var text = 'cat, bat, sat, fat'; // 使用/at/g 在全局中匹配at，并用ond进行替换 var result = text.replace(/at/g, 'ond'); // cond, bond, sond, fond console.log(result);
3. 考虑RegExp对象中捕获组的情况
RegExp具有9个用于存储捕获组的属性。$1, $2...$9，分别用于存储第一到九个匹配的捕获组。我们可以访问这些属性，来获取存储的值。
var text = 'cat, bat, sat, fat'; // 使用/(.at)/g 括号为捕获组，此时只有一个，因此所匹配的值存放在$1中 var result = text.replace(/(.at)/g, '$($1)'); // $(cat), $(bat), $(sat), $(fat) console.log(result);
4. 第二个参数为函数的情况，RegExp对象中不存在捕获组的情况
var text = 'cat, bat, sat, fat';
// 使用/at/g 匹配字符串中所有的at，并将其替换为ond，
// 函数的参数分别为：当前匹配的字符，当前匹配字符的位置，原始字符串
var result = text.replace(/at/g, function(match, pos, originalText) {
console.log(match + ' ' + pos);
return 'ond'
});
console.log(result);
// 输出
/*
at 1 dd.html:12:9
at 6 dd.html:12:9
at 11 dd.html:12:9
at 16 dd.html:12:9
cond, bond, sond, fond dd.html:16:5
*/5. 第二个参数为函数的情况，RegExp对象中存在捕获组的情况
var text = 'cat, bat, sat, fat';
// 使用/(.at)/g 匹配字符串中所有的at，并将其替换为ond，
// 当正则表达式中存在捕获组时，函数的参数一次为：模式匹配项，第一个捕获组的匹配项，
// 第二个捕获组的匹配项...匹配项在字符串中的位置，原始字符串
var result = text.replace(/.(at)/g, function() {
console.log(arguments[0] + ' ' + arguments[1] + ' ' + arguments[2]);
return 'ond'
});
console.log(result);
// 输出
/*
cat at 1
bat at 6
sat at 11
fat at 16
cond, bond, sond, fond
*/以上为replace方法的所有可以使用的情况，下面我们使用replace和正则表达式共同实现字符串trim方法。
(function(myFrame) {
myFrame.trim = function(str) {
// ' hello world '
return str.replace(/(^\s*)|(\s*$)/g, '');
};
window.myFrame = myFrame;
})(window.myFrame || {});
// 测试
var str = ' hello world '
console.log(str.length); // 15
console.log(myFrame.trim(str).length); // 11The above is the detailed content of Detailed introduction to the summary of methods used by replace in javascript. For more information, please follow other related articles on the PHP Chinese website!
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