In the below code, I want to validate messageText with first validationPattern and display the corresponding message from the validationPatterns array. Pattern and Message are separated by Pipe "|" character.
for this I am using the below code and always getting wrong result. Can some one look at this and help me?
var messageText = "Message1234";
var validationPatterns = [
['\/^.{6,7}$/|message one'],
['\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b|message two']
];
for (var i = 0; i < validationPatterns.length; i++) {
var validationvalues = validationPatterns[i].toString();
var expr = validationvalues.split("|")[0];
console.log(expr.constructor);
if(expr.test(messageText)) {
console.log("yes");
} else {
console.log("no");
}
}
I know that we cannot use pipe as separator as pipe is also part of regular expression. However I will change that later.
Your validationpatterns are strings. That means:
The backslashes get eaten as they just string-escape the following characters. "\b" is equivalent to "b". You would need to double escape them: "\\b"
You cannot call the test method on them. You would need to construct RegExp objects out of them.
While it's possible to fix this, it would be better if you just used regex literals and separated them from the message as distinct properties of an object (or in an array).
var inputText = "Message1234";
var validationPatterns = [
[/^.{6,7}$/, 'message one'],
[/\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b/, 'message two']
];
for (var i = 0; i < validationPatterns.length; i++) {
var expr = validationPatterns[i][0],
message = validationPatterns[i][1];
console.log(expr.constructor); // RegExp now, not String
if(expr.test(inputText)) {
console.log(message+": yes");
} else {
console.log(message+": no");
}
}
Your expr variable is still just a string (validationvalues.split("|")[0] will return a string). That's the reason it does not work as a regular expression.
You need to add a line after the initial definition of expr.
expr = new RegExp(expr, 'i');
The 'i' is just an example of how you would use a case-insensitive flag or other flags. Use an empty string if you want a case-sensitive search (the default).
Also, you need to take out the / and / which are surrounding your first pattern. They are only needed when using regular expression literals in JavaScript code, and are not needed when converting strings into regular expressions.
Related
I'm going through an exercise and one of the functions is to write code that takes an input containing only strings and returns the first
non-repeating character.
I've done that already, but i would like to make it smarter by handling any errors that could be a number or symbol. I tried all I could but it seems not to work. It should be purely letters and spaces taken.
Here is what I have so far.
function TheOutput(word){
var a =word.length;
for(var i=0; i < a; i++){
var char=word.charAt(i);
if(word.indexOf(char)===word.lastIndexOf(char)){
result = (char + " is not a number <br/>");
break;
}
return result;
}
}
You can use regular expressions if you want to test if string is containing only letters and spaces.
var onlyLettersAndSpace = 'Valid string';
var stringWithNumbers = 'Invalid string 123';
var RegExpression = new RegExp(/^[a-zA-Z\s]*$/);
console.log(RegExpression.test(onlyLettersAndSpace));
// true
console.log(RegExpression.test(stringWithNumbers));
// false
In your case, you could do something like:
function testWord(word) {
var RegExpression = new RegExp(/^[a-zA-Z\s]*$/);
return RegExpression.test(word);
}
You can do a lot more with regular expressions, see RegExp MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp
I want to check each values from my array if it matches the string,
however it doesn't work when i'm using console.log(/^reg_arr[i]/.test(str1));
but when I use console.log(/^table/.test(str1)); it works
var str1 = 'table football';
var reg_arr = ["table","football"];
for(var i = 0, reg_arr_length = reg_arr.length; i < reg_arr_length; i++)
{
console.log(/^reg_arr[i]/.test(str1)); /* doesnt work */
}
console.log(/^table/.test(str1)); /* this works */
Is there a problem with my syntax,
Thank you,
Use new RegExp(source: string[, flags: string]) (simply RegExp(source: string[, flags: string]) is also working)
var str1 = 'table football';
var reg_arr = ["table","football"];
for(var i = 0, reg_arr_length = reg_arr.length; i < reg_arr_length; i++)
{
console.log(new RegExp(`^${reg_arr[i]}`).test(str1));
}
Using slashes to define a regular expression doesn't allow you to enter variables into the regular expression, that is, in the following example, str1 is checked to contain "test", not the value of the variable test.
var str1 = "hello";
var str2 = "Hello world";
console.log(/str1/i.test(str2))
To solve this issue, you need to create a new regular expression for each value in the array, something that can be done with new RegExp(str), instead of slashes.
var str1 = "hello";
var str2 = "hello world";
console.log(new RegExp(str1, "i").test(str2))
However, this method has a catch, characters from that string are not escaped. So new RegExp("test.hello") will match "test hello", because the dot is interpreted as a regular expression wildcard character and not a period. To fix that, we first have to manually escape any special characters in our search string (unless the things reg_arr are actually regular expressions). I took the code to do that from the middle of this MDN page.
var str1 = "hello"
var str2 = "hello world"
str1.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
console.log(new RegExp(str, "i").test(str2))
So without changing anything else, your final console.log could look like this:
console.log(new RegExp(reg_arr[i].replace(/[.*+?^${}()|[\]\\]/g, '\\$&')).test(str1));
This question already has answers here:
What does the "Nothing to repeat" error mean when using a regex in javascript?
(7 answers)
Closed 4 years ago.
I'm trying to clear a string of any invalid characters to be set as a directory.
Tried a number of methods and this one eventually worked[custom encoding] but now it doesn't, it says "nothing to repeat" in the console. What does that mean? using Chrome.
Here's the code(using random string):
var someTitle = "wa?";
var cleanTitle = cleanTitle(someTitle);
function cleanTitle(title){
var obstructions = ['\\','/',':','*','?','"','<','>','|'];
var solutions = [92,47,58,42,63,34,60,62,124];
var encodedTitle = title;
for (var obstruction = 0; obstruction < obstructions.length; obstruction++){
var char = obstructions[obstruction];
if (encodedTitle.includes(char)){
var enCode = "__i!__"+solutions[obstruction]+"__!i__";
var rEx = new RegExp(char,"g");
encodedTitle = encodedTitle.replace(rEx,enCode);
}
}
console.log("CLEAN: "+title);
console.log("ENCODED: "+encodedTitle);
return encodedTitle;
}
Heres the error:
Uncaught SyntaxError: Invalid regular expression: /?/: Nothing to
repeat
It points to this line -> var rEx = new RegExp(char,"g");
You need to escape some characters when using them as literals in a regular expression. Among those are most of the characters you have in your array.
Given your function replaces the obstruction characters with their ASCII code (and some wrapping __i!__), I would suggest to make your function a bit more concise, by performing the replacement with one regular expression, and a callback passed to .replace():
function cleanTitle(title){
return title.replace(/[\\/:*?"<>|]/g, function (ch) {
return "__i!__"+ch.charCodeAt(0)+"__!i__";
});
}
var someTitle = "wh*r* is |his?";
var result = cleanTitle(someTitle);
console.log(result);
...and if you are in an ES6 compatible environment:
var cleanTitle = t=>t.replace(/[\\/:*?"<>|]/g, c=>"__i!__"+c.charCodeAt(0)+"__!i__");
var someTitle = "wh*r* is |his?";
var result = cleanTitle(someTitle);
console.log(result);
The ? is a regex modifier. When you want to look for it (and build a regex with it), you need to escape it.
That beeing said, a harmless unuseful escaping doesn't hurt (or makes your other search params useable, as there are many modifiers or reserved chars in it) your other search params. So go with
var char = '\\' + obstructions[obstruction];
to replace them all with a (for the regex) string representation
/?/ is not a valid regex. For it to be a regex, you need /\?/.
Regex here would be awkward, as most of the characters need escaping. Instead, consider using a literal string replacement until it is no longer found:
while( encodedTitle.indexOf(char) > -1) {
encodedTitle = encodedTitle.replace(char,enCode);
}
I have strings like this:
ab
rx'
wq''
pok'''
oyu,
mi,,,,
Basically, I want to split the string into two parts. The first part should have the alphabetical characters intact, the second part should have the non-alphabetical characters.
The alphabetical part is guaranteed to be 2-3 lowercase characters between a and z; the non-alphabetical part can be any length, and is gauranteed to only be the characters , or ', but not both in the one string (e.g. eex,', will never occur).
So the result should be:
[ab][]
[rx][']
[wq]['']
[pok][''']
[oyu][,]
[mi][,,,,]
How can I do this? I'm guessing a regular expression but I'm not particularly adept at coming up with them.
Regular expressions have is a nice special called "word boundary" (\b). You can use it, well, to detect the boundary of a word, which is a sequence of alpha-numerical characters.
So all you have to do is
foo.split(/\b/)
For example,
"pok'''".split(/\b/) // ["pok", "'''"]
If you can 100% guarantee that:
Letter-strings are 2 or 3 characters
There are always one or more primes/commas
There is never any empty space before, after or in-between the letters and the marks
(aside from line-break)
You can use:
/^([a-zA-Z]{2,3})('+|,+)$/gm
var arr = /^([a-zA-Z]{2,3})('+|,+)$/gm.exec("pok'''");
arr === ["pok'''", "pok", "'''"];
var arr = /^([a-zA-Z]{2,3})('+|,+)$/gm.exec("baf,,,");
arr === ["baf,,,", "baf", ",,,"];
Of course, save yourself some sanity, and save that RegEx as a var.
And as a warning, if you haven't dealt with RegEx like this:
If a match isn't found -- if you try to match foo','' by mixing marks, or you have 0-1 or 4+ letters, or 0 marks... ...then instead of getting an array back, you'll get null.
So you can do this:
var reg = /^([a-zA-Z]{2,3})('+|,+)$/gm,
string = "foobar'',,''",
result_array = reg.exec(string) || [string];
In this case, the result of the exec is null; by putting the || (or) there, we can return an array that has the original string in it, as index-0.
Why?
Because the result of a successful exec will have 3 slots; [*string*, *letters*, *marks*].
You might be tempted to just read the letters like result_array[1].
But if the match failed and result_array === null, then JavaScript will scream at you for trying null[1].
So returning the array at the end of a failed exec will allow you to get result_array[1] === undefined (ie: there was no match to the pattern, so there are no letters in index-1), rather than a JS error.
You could try something like that:
function splitString(string){
var match1 = null;
var match2 = null;
var stringArray = new Array();
match1 = string.indexOf(',');
match2 = string.indexOf('`');
if(match1 != 0){
stringArray = [string.slice(0,match1-1),string.slice(match1,string.length-1];
}
else if(match2 != 0){
stringArray = [string.slice(0,match2-1),string.slice(match2,string.length-1];
}
else{
stringArray = [string];
}
}
var str = "mi,,,,";
var idx = str.search(/\W/);
if(idx) {
var list = [str.slice(0, idx), str.slice(idx)]
}
You'll have the parts in list[0] and list[1].
P.S. There might be some better ways than this.
yourStr.match(/(\w{2,3})([,']*)/)
if (match = string.match(/^([a-z]{2,3})(,+?$|'+?$)/)) {
match = match.slice(1);
}
Do there exist comprehensive regular expressions that, when applied to JavaScript source code, will match all valid string literals (such as "say \"Hello\"") and regex literals (such as /and\/or/)? The expressions would have to cover all edge cases, including line breaks and escape sequences.
Alternatively, does anyone know of regexes for matching patterns outside of string and regex literals?
My goal is to implement a simple JavaScript syntax extension that allows macros in delimeters (e.g. {{#foo.bar}} or ##foo.bar#) to be expanded by a preprocessor. However, I'd like the macros to be processed only outside of literals.
For now, I'm trying to accomplish this using just string replacement, without having to augment an existing JavaScript lexer/parser.
This JavaScript preprocessor will itself be implemented in JavaScript.
This is the regex that I've been using to match quoted strings which is pretty good since it should work with almost all engines since it does not require backtracking or backreferences or any of that voodoo. This will match all text INSIDE literals.
"(\\.|[^"])*"
Depending on the engine, it might support non capturing groups. In that case you can use
"(?:\\.|[^"])*"
and it should be faster.
I think this is too much for regexes.
Consider var foo = "//" // /"(?:\\.|[^"])*"/. Where do the strings, comments and regex literals start and end? You would need to write a complete JavaScript parser to cover all edge cases. Of course, the parser will be using regexes...
I would probably go about doing something like the following. It will need to be improved for certain possible conditions, though.
var str = '"aaa \"sss \\t bbb" sss #3 ss# ((t sdsds)) ff ';
str += '/gg sdfd \/dsds/ {aaa bbb} {{ss}} {#sdsd#}';
var repeating = ['"','\\\'','/','\\~','\\#'];
// "example" 'example' /example/ ~example~ #example#
var enclosing = [];
enclosing.push(['\\{','\\}']);
enclosing.push(['\\{\\{','\\}\\}']);
enclosing.push(['\\[','\\]']);
enclosing.push(['\\(\\(','\\)\\)']);
// {example} {{example}} [example] ((example))
for (var forEnclosing='',i = 0 ; i < enclosing.length; i++) {
var e = enclosing[i];
var r = e[0]+'(\\\\['+e[0]+e[1]+']|[^'+e[0]+e[1]+'])*'+e[1];
forEnclosing += r + (i < enclosing.length-1 ? '|' : '');
}
for (var forRepeating='',i = 0; i < repeating.length; i++) {
var e = repeating[i];
var r = e+'(\\'+e+'|[^'+e+'])*'+e;
forRepeating += r + (i < repeating.length-1 ? '|' : '');
}
var rx = new RegExp('('+forEnclosing+'|'+forRepeating+')','g');
var m = str.match(rx);
try { for (var i = 0; i < m.length; i++) console.log(m[i]) }
catch(e) {}
Outputs:
"aaa "sss \t bbb"
#3 ss#
((t sdsds))
/gg sdfd /dsds/
{aaa bbb}
{{ss}}
{#sdsd#}
The closest you can get with a regex is to have one regex that matches EITHER a string literal (single- or double-quoted) OR a regex OR a comment (OR whatever else might contain bogus matches) OR one of your macro thingies:
"[^"\\]*(?:\\.[^"\\]*)*"
|
'[^'\\]*(?:\\.[^'\\]*)*'
|
/[^/\\]*(?:\\.[^/\\]*)*/[gim]*
|
/\*[^*]*(?:\*(?!/)[^*]*)*\*/
|
##(\w+\.\w+)#
If group #1 contains anything after the match, it must be what you're looking for. Otherwise, ignore this match and go on to the next one.