Javascript Regexp测试方法奇怪的行为 [英] Javascript Regexp test method weird behaviour
问题描述
我一直在尝试使用正则表达式来评估字符串，但是我注意到了一种奇怪的行为，当我使用正则表达式多次测试时。测试方法在true和false之间交替。
查看此编码器 - > http://codepen.io/gpincheiraa/pen / BoXrEz？editors = 001
I've been trying evaluate a string based in a regular expression, however I noticed a weird behaviour and when I test with the regular expression more than once. The test method alternates between true and false . Check this codepen --> http://codepen.io/gpincheiraa/pen/BoXrEz?editors=001
var emailRegex = /^([a-zA-Z0-9_\.\-]){0,100}\@(([a-zA-Z0-9\-]){0,100}\.)+([a-zA-Z0-9]{2,4})+$/,
phoneChileanRegex = /^\+56\S*\s*9\S*\s*\d{8}(?!\@\w+)/g,
number = "+56982249953";
if(!number.match(phoneChileanRegex) && !number.match(emailRegex) ) {
console.log("it's not a phone number or email address");
}
//Weird Behaviour
console.log(phoneChileanRegex.test(number)); --> true
console.log(phoneChileanRegex.test(number)); --> false
推荐答案
来自 MDN文档：
与
exec（）（或与之结合使用）一样，test（）在同一个全局正则表达式实例上多次调用将超过上一个匹配。
As with
exec()(or in combination with it),test()called multiple times on the same global regular expression instance will advance past the previous match.
所以，第二次调用方法，它会在第一场比赛后寻找一场比赛，即在 +56982249953 之后。没有匹配，因为模式锚定到字符串的开头（ ^ ）（并且因为没有剩下的字符），所以它返回 false 。
So, the second time you call the method, it will look for a match after the first match, i.e. after +56982249953. There is no match because the pattern is anchored to the start of the string (^) (and because there are no characters left), so it returns false.
要完成这项工作，您必须删除 g 修饰符。
To make this work you have to remove the g modifier.
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