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

Answer 1

备用，使用startsWith（）

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

Answer 2

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.

Answer 3

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()"> 

Answer 4

或者，检查'＃'char的索引为0。那么，当我们检查第0个索引时，如果有多个＃字符，这将起作用。

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

Answer 5

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.