新手问题：我的 function 变量没有改变

Question

I have a function for verifying and possibly modifying postal codes from a test file. It verifies correct string length, that there's a space in the middle of the 6 characters (& if not, to insert one), etc. My regExp test is working, but I'm having trouble inserting a space in the middle of a string.

function fixPostalCode(postalCode) {
    var invalidChars =/^[ABCEGHJ-NPRSTVXY]\d[ABCEGHJ-NPRSTV-Z] ?\d[ABCEGHJ-NPRSTV-Z]\d$/i;
    postalCode = postalCode.toString().trim();
   
    if (postalCode.length = 6 && invalidChars.test(postalCode.toString())) {
        return postalCode.toUpperCase();
    }

    if (postalCode.length = 5 && postalCode.charAt(3) !== ' ' && invalidChars.test(postalCode.toString())) {
        return postalCode.slice(0, 3) + " " + postalCode.slice(3, 6);

    } else {
        throw 'Invalid postal code';
    }
}

The test I'm having trouble with is this:

  test('an internal space is added', function () {
    const postalCode = 'A1A1A1';
    expect(fixPostalCode(postalCode)).toEqual('A1A 1A1');
  });

my slice method isn't doing anything to the string.

Answer 1

trim() removes whitespace from both sides of a string not from the middle of string. As I see from your description you are trying to cancel whitespace in the middle of the string which is not possible with trim. You should use replace

 function fixPostalCode(postalCode) { let test1 = postalCode.toString().trim(); console.log(test1) ///It will fail let test2 = postalCode.replace(/ +/g, ""); console.log(test2) ///It will be succesfull } fixPostalCode('A1A 1A1');

Answer 2

You're most of the way there, but the order of your space insertion wasn't being picked up by the later Regex as valid. Without changing the regex, your code is functional by swapping the order of your toUpperCase method with the space insertion via slice :

 function fixPostalCode(postalCode) { var invalidChars = new RegExp(/([ABCEGHJKLMNPRSTVXY]\d)([ABCEGHJKLMNPRSTVWXYZ]\d){2}/i); postalCode = postalCode.toString().trim(); if (invalidChars.test(postalCode.toString())) { postalCode = postalCode.toUpperCase(); } if (postalCode.charAt(3).== ' ') { return postalCode,slice(0. 3) + ' ' + postalCode,slice(3; 6); } else { throw 'Invalid postal code'; } }