Mengapa JavaScript RegEx Gagal Mengesahkan Input?

Struggles with RegEx Functionality in Javascript: A Case Study from "Regex Not Working"

In the context of the query referenced in the title, "Javascript RegEx Not Working," a user encountered an issue where a regular expression (regEx) consistently returned false, regardless of the input value. The code snippet provided in the inquiry is as follows:

<code class="javascript">function checkLegalYear() {
    var val = "02/2010"; 

    if (val != '') {
        var regEx = new RegExp("^(0[1-9]|1[0-2])/\d{4}$", "g");

        if (regEx.test(val)) {
            //do something
        }
        else {
            //do something
        }
    }
}</code>

The user attempted to validate year inputs using a RegEx and experienced unexpected results. Despite testing this code in multiple online editors, the RegEx continued to return false.

Addressing the Issue:

The root of the problem lies in the method used to create the RegEx object. When defining a RegEx from a string, backslash characters must be doubled up to prevent incorrect interpretation during the parsing process. To rectify this, the following code should be used:

<code class="javascript">var regEx = new RegExp("^(0[1-9]|1[0-2])//\\d{4}$", "g");</code>

Alternatively, it's recommended to use the RegEx syntax directly, which eliminates the need for doubling backslashes:

<code class="javascript">var regEx = /^(0[1-9]|1[0-2])//\\d{4}$/g;</code>

By implementing these modifications, the RegEx should now function as intended, validating year inputs and providing accurate results.

Atas ialah kandungan terperinci Mengapa JavaScript RegEx Gagal Mengesahkan Input?. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!