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I write a small parser for a custom query language which contains Chinese characters. When detecting syntax error, it outputs error message as following:

語法錯誤：應為數，但為字串。
索引 = '3213茂訊'"
       ^

The last line has only one '^' character to indicate the position of error token. For Chinese characters' visual length occupy two other characters, I need to detect wide character to calculate the '^' position to indicate the right token. Does anyone knows some function can detect the wide character in javascript?

Fhope Cc
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1 Answers1

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I’m not sure if I understand you correct. But you might want to try the https://www.npmjs.com/package/wcwidth package. Which can be implemented as follows:

import wcwidth from 'wcwidth';

const getCharAtPosition = (str, position) => {
  let currPos = 0;
  return [...str].find(char => {
    const charWidth = wcwidth(char);
    const isPosition =
      currPos === position || (charWidth === 2 && currPos === position - 1);
    currPos += charWidth;
    return isPosition;
  });
};

const indicatorPos = '       ^'.indexOf('^');
console.log(getCharAtPosition(`索引 = '3213茂訊'"`, indicatorPos));
// will log: '

I didn’t test it, but something like this might work.

Leif Marcus
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