Develop Reference

replace \r\n with < br /> as text

Trying for 2 hours to replace \r\n with < br/> but it seems to be impossible.
I don't know what i'm doing! Please help!
const text = '"Hello!\r\n\r\nThis is a dog!'
const checkText = str=> {
const match = /\r|\n/.exec(text);
if (match) {
//return str.replace(/(?:\\[rn]|[\r\n]+)+/g, '<br/>');
return str.replace('/r/n', '<br/>');
}
return str;
};
checkText(text)

Just do this:
text.replace(/\r\n/g, '<br/>');

Covering all the possible new line character combinations.
String tmp = s.replaceAll("\r\n", "<br>"); // Windows
tmp = tmp.replaceAll("\r", "<br>"); // Old MAC
return tmp.replaceAll("\n", "<br>"); // Linux / UNIX

You may try:
(text+ '').replace(/([^>\r\n]?)(\r\n|\n\r|\r|\n)/g, '$1<br/>$2');

There are multiple things wrong with your code:
String.prototype.replace only replaces the first occurrence of a string. You need to use a regex argument with the /g flag to replace all occurrences.
Escapes use a backslash, not a forward slash: Use \r\n, not /r/n.
checkText returns a string, but your call-site doesn't do anything with the returned string - it's just dropped. Strings are immutable in JavaScript.
I don't recommend using strings to hold HTML because it can (very easily) cause HTML-injection (including <script>-injection) attacks.
Instead, do one of the following:
Use String.prototype.split and HTML-encode each string in the array and join with "<br />".
Add the string directly to the document with .textContent (don't use innerText anymore) and give the parent element the CSS style whitespace: pre-wrap;.

ASCII character not being recognized in if statement

I am trying to get a string from a html page with jquery and this is what I have.
var text = $(this).text();
var key = text.substring(0,1);
if(key == ' ' || key == ' ')
key = text.substring(1,2);
text is this  Home
And I want to skip the space and or the keycode above It appears this code does not work either. It only gets the text.substring(0,1); instead of text.substring(1,2); because the if statement is not catching.= and I am not sure why. Any help would be super awesome! Thanks!

There are several problems with the code in the question. First,   has no special meaning in JavaScript: it is a string literal with six characters. Second, text.substring(1,2) returns simply the second character of text, not all characters from the second one onwards.
Assuming that you wish to remove one leading SPACE or NO-BREAK SPACE (which is what   means in HTML; it is not an Ascii character, by the way), then the following code would work:
var first = text.substring(0, 1);
if(first === ' ' || first === '\u00A0') {
text = text.substring(1, text.length);
}
The notation \u00A0 is a JavaScript escape notation for NO-BREAK SPACE U+00A0.
Should you wish to remove multiple spaces at the start, and perhaps at the end too, some modifications are needed. In that case, using a replace operation with regular expression is probably best.

If you want remove spaces at the beginning (and end) of a string, you can use the trim function
var myvar = " home"
myVar.trim() // --> "home"
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/Trim

How can I convert a string into a unicode character?

In Javascript '\uXXXX' returns in a unicode character. But how can I get a unicode character when the XXXX part is a variable?
For example:
var input = '2122';
console.log('\\u' + input); // returns a string: "\u2122"
console.log(new String('\\u' + input)); // returns a string: "\u2122"
The only way I can think of to make it work, is to use eval; yet I hope there's a better solution:
var input = '2122';
var char = '\\u' + input;
console.log(eval("'" + char + "'")); // returns a character: "™"

Use String.fromCharCode() like this: String.fromCharCode(parseInt(input,16)). When you put a Unicode value in a string using \u, it is interpreted as a hexdecimal value, so you need to specify the base (16) when using parseInt.

String.fromCharCode("0x" + input)
or
String.fromCharCode(parseInt(input, 16)) as they are 16bit numbers (UTF-16)

JavaScript uses UCS-2 internally.
Thus, String.fromCharCode(codePoint) won’t work for supplementary Unicode characters. If codePoint is 119558 (0x1D306, for the '𝌆' character), for example.
If you want to create a string based on a non-BMP Unicode code point, you could use Punycode.js’s utility functions to convert between UCS-2 strings and UTF-16 code points:
// `String.fromCharCode` replacement that doesn’t make you enter the surrogate halves separately
punycode.ucs2.encode([0x1d306]); // '𝌆'
punycode.ucs2.encode([119558]); // '𝌆'
punycode.ucs2.encode([97, 98, 99]); // 'abc'

Since ES5 you can use
String.fromCodePoint(number)
to get unicode values bigger than 0xFFFF.
So, in every new browser, you can write it in this way:
var input = '2122';
console.log(String.fromCodePoint(input));
or if it is a hex number:
var input = '2122';
console.log(String.fromCodePoint(parseInt(input, 16)));
More info:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCodePoint
Edit (2021):
fromCodePoint is not just used for bigger numbers, but also to combine Unicode emojis.
For example, to draw a waving hand, you have to write:
String.fromCodePoint(0x1F44B);
But if you want a waving hand with a skin tone, you have to combine it:
String.fromCodePoint(0x1F44B, 0x1F3FC);
In future (or from now), you will even be able to combine 2 emoji to create a new one, for example a heart and a fire, to create a burning heart:
String.fromCodePoint(0x2764, 0xFE0F, 0x200D, 0x1F525);
32-bit number:
<script>
document.write(String.fromCodePoint(0x1F44B));
</script>
<br>
32-bit number + skin:
<script>
document.write(String.fromCodePoint(0x1F44B, 0x1F3FE));
</script>
<br>
32-bit number + another emoji:
<script>
document.write(String.fromCodePoint(0x2764, 0xFE0F, 0x200D, 0x1F525));
</script>

var hex = '2122';
var char = unescape('%u' + hex);
console.log(char);
will returns " ™ "

How to replace whitespaces using javascript?

I'm trying to remove the whitespaces from a textarea . The below code is not appending the text i'm selecting from two dropdowns. Can somebody tell me where i'd gone wrong? I'm trying to remove multiple spaces within the string as well, will that work with the same? Dont know regular expressions much. Please help.
function addToExpressionPreview() {
var reqColumnName = $('#ddlColumnNames')[0].value;
var reqOperator = $('#ddOperator')[0].value;
var expressionTextArea = document.getElementById("expressionPreview");
var txt = document.createTextNode(reqColumnName + reqOperator.toString());
if (expressionTextArea.value.match(/^\s+$/) != null)
{
expressionTextArea.value = (expressionTextArea.value.replace(/^\W+/, '')).replace(/\W+$/, '');
}
expressionTextArea.appendChild(txt);
}

> function addToExpressionPreview() {
> var reqColumnName = $('#ddlColumnNames')[0].value;
> var reqOperator = $('#ddOperator')[0].value;
You might as well use document.getElementById() for each of the above.
> var expressionTextArea = document.getElementById("expressionPreview");
> var txt = document.createTextNode(reqColumnName + reqOperator.toString());
reqOperator is already a string, and in any case, the use of the + operator will coerce it to String unless all expressions or identifiers involved are Numbers.
> if (expressionTextArea.value.match(/^\s+$/) != null) {
There is no need for match here. I seems like you are trying to see if the value is all whitespace, so you can use:
if (/^\s*$/.test(expressionTextArea.value)) {
// value is empty or all whitespace
Since you re-use expressionTextArea.value several times, it would be much more convenient to store it an a variable, preferably with a short name.
> expressionTextArea.value = (expressionTextArea.value.replace(/^\W+/,
> '')).replace(/\W+$/, '');
That will replace one or more non-word characters at the end of the string with nothing. If you want to replace multiple white space characters anywhere in the string with one, then (note wrapping for posting here):
expressionTextArea.value = expressionTextArea.value.
replace(/^\s+/,'').
replace(/\s+$/, '').
replace(/\s+/g,' ');
Note that \s does not match the same range of 'whitespace' characters in all browsers. However, for simple use for form element values it is probably sufficient.

Whitespace is matched by \s, so
expressionTextArea.value.replace(/\s/g, "");
should do the trick for you.
In your sample, ^\W+ will only match leading characters that are not a word character, and ^\s+$ will only match if the entire string is whitespace. To do a global replace(not just the first match) you need to use the g modifier.

Refer this link, you can get some idea. Try .replace(/ /g,"UrReplacement");
Edit: or .split(' ').join('UrReplacement') if you have an aversion to REs

JavaScript Replace - u0009 .... with .replace(/\u0009/g,'');

I'd like to use Javascript to replace all instances of \u009 in a string
This doesn't seem to be working: .replace(/\u0009/g,'');
Do I need to escape something?

First, the question says "replace all instances of \u009 in a string".
But, the regex has replace(/\u0009/g,''); Is this a typo (different number of zeroes)?
Anyway, if the string only contains, unicode, horizontal tab characters (just one char), then the regex is fine.
If it actually contains 6 ascii chars, then the regex needs to be escaped, like so:
var oneChar = 'Pre \u0009 post';
var sixChars = 'Pre \\u0009 post';
//-- NOTE: If not using Firebug, replace 'console.log()' with 'alert()'.
console.log (oneChar + ' becomes --> ' + oneChar.replace (/\u0009/g, "") );
console.log (sixChars + ' becomes --> ' + sixChars.replace (/\\u0009/g, "") );

You need another escape .replace(/\\u009/g,''); :)