How to use regular expression to validate Chinese input?

Question

The thing is I need to treat this kind of Chinese input as invalid in client side validation:

Input is invalid when any English character mixed with any Chinese character and spaces has a total length >=10.

Let's say : "你的a你的a你的a你" or "你的 你的 你的 你" (length is 10) is invalid. But "你的a你的a你的a" (length is 9) is OK.

I am using both Javascript to do client side validation and Java to do the server side. So I suppose applying the regular expression on both should be perfect.

Can anyone give some hints how to write the rules in regular expression?

Answer 1

From What's the complete range for Chinese characters in Unicode?, the CJK unicode ranges are:

Block                                   Range       Comment
--------------------------------------- ----------- ----------------------------------------------------
CJK Unified Ideographs                  4E00-9FFF   Common
CJK Unified Ideographs Extension A      3400-4DBF   Rare
CJK Unified Ideographs Extension B      20000-2A6DF Rare, historic
CJK Unified Ideographs Extension C      2A700–2B73F Rare, historic
CJK Unified Ideographs Extension D      2B740–2B81F Uncommon, some in current use
CJK Unified Ideographs Extension E      2B820–2CEAF Rare, historic
CJK Compatibility Ideographs            F900-FAFF   Duplicates, unifiable variants, corporate characters
CJK Compatibility Ideographs Supplement 2F800-2FA1F Unifiable variants
CJK Symbols and Punctuation             3000-303F

You probably want to allow code points from the Unicode blocks CJK Unified Ideographs and CJK Unified Ideographs Extension A.

This regex will match 0 to 9 spaces, ideographic spaces (U+3000), A-Z letters, or code points in those 2 CJK blocks.

/^[ A-Za-z\u3000-\u303F\u3400-\u4DBF\u4E00-\u9FFF]{0,9}$/

The ideographs are listed in:

• part 1
• part 2
• part 3
• part 4
• Extension A

However, you may as well add more blocks.

Code:

function has10OrLessCJK(text) {
    return /^[ A-Za-z\u3000-\u303F\u3400-\u4DBF\u4E00-\u9FFF]{0,9}$/.test(text);
}

function checkValidation(value) {
    var valid = document.getElementById("valid");
    if (has10OrLessCJK(value)) {
        valid.innerText = "Valid";
    } else {
        valid.innerText = "Invalid";
    }
}

<input type="text" 
       style="width:100%"
       oninput="checkValidation(this.value)"
       value="你的a你的a你的a">

<div id="valid">
    Valid
</div>