Check a certain section of string if it contains a substring

Question

I want to check a certain section of my string if it contains a substring.

This is my code so far:

var sHexValue = document.getElementById("ColourInput").value;
fnDebugMessage(sHexValue);

if (sHexValue.includes("#", 0)) {
  fnDebugMessage("TRUE");
}

So currently it checks the ColourInput if it contains # from the position 0 in the string, however I want to restrict it so it checks only the first character of ColourInput

How do I do this? Any help is appreciated

so you want to check if the first character in `sHexValue` is a `#`? You can do: `sHexValue[0] === "#"` if that's the case — Nick Parsons, Mar 14 '19 at 11:03
You can check the characters in a string in a similar manner to an array. I.e, `sHexValue[0] === '#'`? — Lewis, Mar 14 '19 at 11:03
Possible duplicate of [How to get first character of string?](https://stackoverflow.com/questions/3427132/how-to-get-first-character-of-string) and [Check First Char In String](https://stackoverflow.com/questions/6348325) and [How to get first letter from string using jquery](https://stackoverflow.com/questions/18887742) — adiga, Mar 14 '19 at 11:03

score 2 · Accepted Answer · answered Mar 14 '19 at 11:18

2

Alternate, using startsWith()

document.getElementById("ColourInput").value.startsWith('#')

answered Mar 14 '19 at 11:18

User863

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Oh ok, I didn't know there is actually a command to check if a string starts with a character – User0123456789 Mar 14 '19 at 11:22

score 1 · Answer 2 · answered Mar 14 '19 at 11:03

1

Use this to get first element:

 document.getElementById("ColourInput").value.charAt(0) === "#"

This will check only the first character of the value if it is '#' which is what you are looking for, if I understand correctly.

answered Mar 14 '19 at 11:03

Stanimirovv

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Kamil Kiełczewski · Answer 3 · 2019-03-14T11:21:24.600

1

Try regexp

/^#/.test(sHexValue)

for full hex color use this

/^#[A-Fa-f0-9]{6}$/

function check() {
  let sHexValue = document.getElementById("ColourInput").value;
  let msg="Not contains: #";

  if(/^#/.test(sHexValue)) msg="contains: #";

  console.log(msg);

  if(/^#[A-Fa-f0-9]{6}$/.test(sHexValue)) console.log("Color :)");
}

<input id="ColourInput" onkeyup="check()">

edited Mar 14 '19 at 11:21

answered Mar 14 '19 at 11:10

Kamil Kiełczewski

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Well this it will return true in position of #. – Rahul Raut Mar 14 '19 at 11:14

Rahul Raut · Answer 4 · 2019-03-14T18:06:28.063

1

Alternate way, check index of '#' char is 0. Well this will work in case of multiple # characters as we are checking for 0th index.

 document.getElementById("ColourInput").value.indexOf('#') === 0

edited Mar 14 '19 at 18:06

answered Mar 14 '19 at 11:12

Rahul Raut

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score 1 · Answer 5 · answered Mar 14 '19 at 11:18

1

Use this code to check if the index of char in string is 0.

sHexValue.indexOf("#") === 0

Note : includes() method may not be supported in IE browser. so just check with this method and let me know if you face after this. Thanks.

answered Mar 14 '19 at 11:18

Harsh_Jani

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Check a certain section of string if it contains a substring

5 Answers5