I am very new to making search text in array some elements in array are in rangers i.e it cant be anything after certain text in this AA and A regex and I have multi-dimensional array and I want search text in each array . So I wrote something like this.I put AA* in array so only first 2 character should match and A* for only one character match.
arr = [
["AA*","ABC","XYZ"] ,
["A*","AXY","AAJ"]
]
var text = "AA3";
for ($i=0; $i<arr.length; $i++ ){
var new_array = [];
new_array = arr[$i];
new_array.filter(function(array_element) {
var result = new RegExp(array_element).test(text);
if( result == true){
console.log(arr[$i]);
}
});
}
So what i want is when text = "AA3" or anything after double A AA[anything] and the output should be first array which is ["AA*","ABC","XYZ"] but I am getting both array as output and when text = "A3" then output should be second array which is ["A*","POI","LKJ"] but I am getting both array.But if text = "ABC" or text = "AAJ" then it should output first array or second array respectively.I dont know anything about how to write regex or is there anyway I can implement this using any other method.
Thanks in advance any advice will be helpful.
Summary
In short, the issue is "*"! The * found in the members of the set array is why you're getting the same array each time.
Detailed Info
Regexp is a one concept most developers find hard to understand (I am one of such btw 😅).
I'll start off with an excerpt intro to Regexp on MDN
Regexp are patterns used to match character combinations in strings - MDN
With that in mind you want to understand what goes on with your code.
When you create a Regex like /A*/ to test "AA3", what would be matched would be A, AA, etc. This is a truthy in javascript. You would want a more stricter matching with ^ or $ or strictly matching a number with \d.
I rewrote your code as a function below:
arr = [
["AA*", "ABC", "XYZ"],
["A*", "AXY", "AAJ"],
];
findInArray(arr, "AA3") // prints both array
findInArray(arr, "AAJ") // prints second array
findInArray(arr, "ABC") // prints first array
function findInArray(array, value) {
return array.filter((subArray) =>
subArray.some((item) => {
const check = new RegExp(value);
return check.test(item);
})
);
}
Problem
The problem lies in the fact you use each of the strings as a regex.
For a string with a * wildcard, this evaluates to zero or more matches of the immediately preceding item, which will always be true.
For a string consisting solely of alphanumerics, this is comparing a string to itself, which similarly will always give true.
For strings containing characters that constitute the regex's syntax definition, this could result in errors or unintended behavior.
MDN article on RegExp quantifiers
Rewrite
Assumptions:
The value with a * wildcard is always only at the 0th position,
There is only one such wildcard in its string,
The question mentions that for text = 'AAJ' only the 2nd array shall be returned, but both the AA* from the 1st array and AAJ from the 2nd would seem to match this text.
As such, I assume the wildcard can only stand for a number (as other examples seem to suggest).
Code:
const abc = (arrs, text) => {
return arrs.filter(arr => {
const regex = new RegExp(`^${arr[0].replace('*', '\\d+')}$`);
return regex.test(text) || arr.includes(text);
})
}
const arr = [
["AA*", "ABC", "XYZ"],
["A*", "AXY", "AAJ"]
];
console.log(
`1=[${abc(arr, "AA3")}]
2=[${abc(arr, "ABC")}]
3=[${abc(arr, "AAJ")}]`);
Related
I Would like to extract the Twitter handler names from a text string, using a regex. I believe I am almost there, except for the ">" that I am including in my output. How can I change my regex to be better, and drop the ">" from my output?
Here is an example of a text string value:
"PlaymakersZA, Absa, DiepslootMTB"
The desired output would be an array consisting of the following:
PlaymakersZA, Absa, DiepslootMTB
Here is an example of my regex:
var array = str.match(/>[a-z-_]+/ig)
Thank you!
You can use match groups in your regex to indicate the part you wish to extract.
I set up this JSFiddle to demonstrate.
Basically, you surround the part of the regex that you want to extract in parenthesis: />([a-z-_]+)/ig, save it as an object, and execute .exec() as long as there are still values. Using index 1 from the resulting array, you can find the first match group's result. Index 0 is the whole regex, and next indices would be subsequent match groups, if available.
var str = "PlaymakersZA, Absa, DiepslootMTB";
var regex = />([a-z-_]+)/ig
var array = regex.exec(str);
while (array != null) {
alert(array[1]);
array = regex.exec(str);
}
You could just strip all the HTML
var str = "PlaymakersZA, Absa, DiepslootMTB";
$handlers = str.replace(/<[^>]*>|\s/g,'').split(",");
I'm trying to split a TitleCase (or camelCase) string into precisely two parts using javascript. I know I can split it into multiple parts by using the lookahead:
"StringToSplit".split(/(?=[A-Z])/);
And it will make an array ['String', 'To', 'Split']
But what I need is to break it into precisely TWO parts, to produce an array like this:
['StringTo', 'Split']
Where the second element is always the last word in the TitleCase, and the first element is everything else that precedes it.
Is this what you are looking for ?
"StringToSplit".split(/(?=[A-Z][a-z]+$)/); // ["StringTo", "Split"]
Improved based on lolol answer :
"StringToSplit".split(/(?=[A-Z][^A-Z]+$)/); // ["StringTo", "Split"]
Use it like this:
s = "StringToSplit";
last = s.replace(/^.*?([A-Z][a-z]+)(?=$)/, '$1'); // Split
first = s.replace(last, ''); // StringTo
tok = [first, last]; // ["StringTo", "Split"]
You could use
(function(){
return [this.slice(0,this.length-1).join(''), this[this.length-1]];
}).call("StringToSplit".split(/(?=[A-Z])/));
//=> ["StringTo", "Split"]
In [other] words:
create the Array using split from a String
join a slice of that Array without the last element of that
Array
add that and the last element to a final Array
I don't understand this behaviour:
var string = 'a,b,c,d,e:10.';
var array = string.split ('.');
I expect this:
console.log (array); // ['a,b,c,d,e:10']
console.log (array.length); // 1
but I get this:
console.log (array); // ['a,b,c,d,e:10', '']
console.log (array.length); // 2
Why two elements are returned instead of one? How does split work?
Is there another way to do this?
You could add a filter to exclude the empty string.
var string = 'a,b,c,d,e:10.';
var array = string.split ('.').filter(function(el) {return el.length != 0});
A slightly easier version of #xdazz version for excluding empty strings (using ES6 arrow function):
var array = string.split('.').filter(x => x);
This is the correct and expected behavior. Given that you've included the separator in the string, the split function (simplified) takes the part to the left of the separator ("a,b,c,d,e:10") as the first element and the part to the rest of the separator (an empty string) as the second element.
If you're really curious about how split() works, you can check out pages 148 and 149 of the ECMA spec (ECMA 262) at http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf
Use String.split() method with Array.filter() method.
var string = 'a,b,c,d,e:10.';
var array = string.split ('.').filter(item => item);
console.log(array); // [a,b,c,d,e:10]
console.log (array.length); // 1
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/split
trim the trailing period first
'a,b,c,d,e:10.'.replace(/\.$/g,''); // gives "a,b,c,d,e:10"
then split the string
var array = 'a,b,c,d,e:10.'.replace(/\.$/g,'').split('.');
console.log (array.length); // 1
That's because the string ends with the . character - the second item of the array is empty.
If the string won't contain . at all, you will have the desired one item array.
The split() method works like this as far as I can explain in simple words:
Look for the given string to split by in the given string. If not found, return one item array with the whole string.
If found, iterate over the given string taking the characters between each two occurrences of the string to split by.
In case the given string starts with the string to split by, the first item of the result array will be empty.
In case the given string ends with the string to split by, the last item of the result array will be empty.
It's explained more technically here, it's pretty much the same for all browsers.
According to MDN web docs:
Note: When the string is empty, split() returns an array containing
one empty string, rather than an empty array. If the string and
separator are both empty strings, an empty array is returned.
const myString = '';
const splits = myString.split();
console.log(splits);
// ↪ [""]
Well, split does what it is made to do, it splits your string. Just that the second part of the split is empty.
Because your string is composed of 2 part :
1 : a,b,c,d,e:10
2 : empty
If you try without the dot at the end :
var string = 'a,b,c:10';
var array = string.split ('.');
output is :
["a,b,c:10"]
You have a string with one "." in it and when you use string.split('.') you receive array containing first element with the string content before "." character and the second element with the content of the string after the "." - which is in this case empty string.
So, this behavior is normal. What did you want to achieve by using this string.split?
try this
javascript gives two arrays by split function, then
var Val = "abc#gmail.com";
var mail = Val.split('#');
if(mail[0] && mail[1]) { alert('valid'); }
else { alert('Enter valid email id'); valid=0; }
if both array contains length greater than 0 then condition will true
Suppose I have to access a some pattern of digit using javascript. Please have a look.
For Example :: Pattern needed :: Fomat - $12.00 only
If user enters the value 123.12 => Output = $123.12
If user enters the value 123.1 => Output = $123.10
If user enters the value 123.1237 => Output = $123.12 :: Here I am unable to get the first two element of second array having value as 1237.
Thanks
Why not:
var number = 123.1237;
var dollarAmount = number.toFixed(2);
console.log(dollarAmount);
Nasty string manipulation is not the answer here.
If you have '123.1237 as a string input, then input.split('.') would give you an array with two strings 123 and 1237. Thus what you really want to do is sub-string the second string to get the first two characters:
1237.subsring(0, 2);
I need to do a lot of regex things in javascript but am having some issues with the syntax and I can't seem to find a definitive resource on this.. for some reason when I do:
var tesst = "afskfsd33j"
var test = tesst.match(/a(.*)j/);
alert (test)
it shows
"afskfsd33j, fskfsd33"
I'm not sure why its giving this output of original and the matched string, I am wondering how I can get it to just give the match (essentially extracting the part I want from the original string)
Thanks for any advice
match returns an array.
The default string representation of an array in JavaScript is the elements of the array separated by commas. In this case the desired result is in the second element of the array:
var tesst = "afskfsd33j"
var test = tesst.match(/a(.*)j/);
alert (test[1]);
Each group defined by parenthesis () is captured during processing and each captured group content is pushed into result array in same order as groups within pattern starts. See more on http://www.regular-expressions.info/brackets.html and http://www.regular-expressions.info/refcapture.html (choose right language to see supported features)
var source = "afskfsd33j"
var result = source.match(/a(.*)j/);
result: ["afskfsd33j", "fskfsd33"]
The reason why you received this exact result is following:
First value in array is the first found string which confirms the entire pattern. So it should definitely start with "a" followed by any number of any characters and ends with first "j" char after starting "a".
Second value in array is captured group defined by parenthesis. In your case group contain entire pattern match without content defined outside parenthesis, so exactly "fskfsd33".
If you want to get rid of second value in array you may define pattern like this:
/a(?:.*)j/
where "?:" means that group of chars which match the content in parenthesis will not be part of resulting array.
Other options might be in this simple case to write pattern without any group because it is not necessary to use group at all:
/a.*j/
If you want to just check whether source text matches the pattern and does not care about which text it found than you may try:
var result = /a.*j/.test(source);
The result should return then only true|false values. For more info see http://www.javascriptkit.com/javatutors/re3.shtml
I think your problem is that the match method is returning an array. The 0th item in the array is the original string, the 1st thru nth items correspond to the 1st through nth matched parenthesised items. Your "alert()" call is showing the entire array.
Just get rid of the parenthesis and that will give you an array with one element and:
Change this line
var test = tesst.match(/a(.*)j/);
To this
var test = tesst.match(/a.*j/);
If you add parenthesis the match() function will find two match for you one for whole expression and one for the expression inside the parenthesis
Also according to developer.mozilla.org docs :
If you only want the first match found, you might want to use
RegExp.exec() instead.
You can use the below code:
RegExp(/a.*j/).exec("afskfsd33j")
I've just had the same problem.
You only get the text twice in your result if you include a match group (in brackets) and the 'g' (global) modifier.
The first item always is the first result, normally OK when using match(reg) on a short string, however when using a construct like:
while ((result = reg.exec(string)) !== null){
console.log(result);
}
the results are a little different.
Try the following code:
var regEx = new RegExp('([0-9]+ (cat|fish))','g'), sampleString="1 cat and 2 fish";
var result = sample_string.match(regEx);
console.log(JSON.stringify(result));
// ["1 cat","2 fish"]
var reg = new RegExp('[0-9]+ (cat|fish)','g'), sampleString="1 cat and 2 fish";
while ((result = reg.exec(sampleString)) !== null) {
console.dir(JSON.stringify(result))
};
// '["1 cat","cat"]'
// '["2 fish","fish"]'
var reg = new RegExp('([0-9]+ (cat|fish))','g'), sampleString="1 cat and 2 fish";
while ((result = reg.exec(sampleString)) !== null){
console.dir(JSON.stringify(result))
};
// '["1 cat","1 cat","cat"]'
// '["2 fish","2 fish","fish"]'
(tested on recent V8 - Chrome, Node.js)
The best answer is currently a comment which I can't upvote, so credit to #Mic.