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
– Nick Parsons, Commented Mar 14, 2019 at 11:03
You can check the characters in a string in a similar manner to an array. I.e, sHexValue[0] === '#'? — Someone
– Someone, Commented Mar 14, 2019 at 11:03
Possible duplicate of How to get first character of string? and Check First Char In String and How to get first letter from string using jquery — adiga
– adiga, Commented Mar 14, 2019 at 11:03

User863 · Accepted Answer · 2019-03-14 11:18:00Z

2

Alternate, using startsWith()

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

answered Mar 14, 2019 at 11:18

User863

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User0123456789 Over a year ago

Oh ok, I didn't know there is actually a command to check if a string starts with a character

Stanimirovv · Accepted Answer · 2019-03-14 11:03:30Z

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, 2019 at 11:03

Stanimirovv

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Comments

Harsh_Jani · Accepted Answer · 2019-03-14 11:18:29Z

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, 2019 at 11:18

Harsh_Jani

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Kamil Kiełczewski · Accepted Answer · 2019-03-14 11:21:24Z

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, 2019 at 11:21

answered Mar 14, 2019 at 11:10

Kamil Kiełczewski

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1 Comment

Rahul Raut Over a year ago

Well this it will return true in position of #.

Rahul Raut · Accepted Answer · 2019-03-14 18:06:28Z

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, 2019 at 18:06

answered Mar 14, 2019 at 11:12

Rahul Raut

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