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Why Does My If Statement Only Work When The Logic is Also Console Logged? [duplicate]

This question already has answers here:
Why does a RegExp with global flag give wrong results?
(7 answers)
Closed 3 years ago.
The logic for testing a string agains a regex is only working when the if statement is preceded by a console.log including matching logic.
I have tried directly using the value returned from this.props, rewriting the code into an if/else if statement, reordering the statements, removing other statements, changing the logic in the console.log.
const operatorRegex = /[+]|[-]|[*]|[/]/g,
equalsRegex = /[=]/g,
numberRegex = /[\d]/g,
decimalRegex = /[.]/g,
currentSumLength = this.props.inputSeq.length,
currInput = e.target.textContent,
firstChar = this.props.inputSeq[0],
prevSum = this.props.prevSum,
prevChar = this.props.lastInput;
if(operatorRegex.test(currInput)) {
if((currentSumLength === 0) && (prevSum === '')) {
alert('Why you starting a sum with an operator?');
}
console.log(operatorRegex.test(prevChar))
if(operatorRegex.test(prevChar)) {
alert('Two in a row');
}
this.props.inputOperator(currInput)
} else if (Other logic) {
Other Code
}
When the user inputs two operators (+,-,/,=) it should alert with the error.

TL;DR: Remove the g modifier in the regex since you are only testing one char at a time
This is due to an interesting side-effect of the global modifier of the regular expression.
Because you use the g modifier, the regular expression (operatorRegex) will keep a state of the lastIndex it matched.
Example:
const regex = /cat/g
const str = "catcat"
console.log(regex.test(str)) // True
// It found the first "cat" and set the internal `lastIndex` to 3.
console.log(regex.test(str)) // True
// It found the second "cat" and set the internal `lastIndex` to 6.
console.log(regex.test(str)) // False
// It couldn't find a "cat" after the index 6.
// It then set `lastIndex` back to 0
console.log(regex.test(str)) // True again
So, as we can see: when running multiple time the same regex, we can have different results because of the statefulness!
However, if we do not specify the g modifier, the regex will not change the lastIndex attribute, therefore will not be stateful.

How to access the first two digits of a number

I want to access the first two digits of a number, and i have tried using substring, substr and slice but none of them work. It's throwing an error saying substring is not defined.
render() {
let trial123 = this.props.buildInfo["abc.version"];
var str = trial123.toString();
var strFirstThree = str.substring(0,3);
console.log(strFirstThree);
}
I have tried the above code
output of(above code)
trial123=19.0.0.1
I need only 19.0
How can i achieve this?

I would split it by dot and then take the first two elements:
const trial = "19.0.0.1"
console.log(trial.split(".").slice(0, 2).join("."))
// 19.0

You could just split and then join:
const [ first, second ] = trial123.split('.');
const result = [ first, second ].join('.');

I have added a code snippet of the work: (explanation comes after it, line by line).
function getFakePropValue(){
return Math.round(Math.random()) == 0 ? "19.0.0.1" : null;
}
let trial123 = getFakePropValue() || "";
//var str = trial123.toString();
// is the toString() really necessary? aren't you passing it along as a String already?
var strFirstThree = trial123.split('.');
//var strFirstThree = str.substring(0,3);
//I wouldn't use substring , what if the address 191.0.0.1 ?
if(strFirstThree.length >= 2)
console.log(strFirstThree.splice(0,2).join("."));
else
console.error("prop was empty");
Because you are using React, the props value was faked with the function getFakePropValue. The code inside is irrelevant, what I am doing is returning a String randomly, in case you have allowed in your React Component for the prop to be empty. This is to show how you an create minimal robust code to avoid having exceptions.
Moving on, the following is a safety net to make sure the variable trial123 always has a string value, even if it's "".
let trial123 = getFakePropValue() || "";
That means that if the function returns something like null , the boolean expression will execute the second apart, and return an empty string "" and that will be the value for trial123.
Moving on, the line where you convert to toString I have removed, I assume you are already getting the value in string format. Next.
var strFirstThree = trial123.split('.');
That creates an array where each position holds a part of the IP addrss. So 19.0.0.1 would become [19,0,0,1] that's thanks to the split by the delimiter . . Next.
if(strFirstThree.length >= 2)
console.log(strFirstThree.splice(0,2).join("."));
else
console.error("prop was empty");
This last piece of code uses the conditional if to make sure that my array has values before I try to splice it and join. The conditional is not to avoid an exception, since splice and join on empty arrays just returns an empty string. It's rather for you to be able to raise an error or something if needed. So if the array has values, I keep the first two positions with splice(0,2) and then join that array with a '.'. I recommend it more than the substr method you were going for because what if you get a number that's 191.0.0.1 then the substr would return the wrong string back, but with splice and join that would never happen.
Things to improve
I would strongly suggest using more human comprehensible variables (reflect their use in the code)
The right path for prop value checking is through Prop.Types, super easy to use, very helpful.
Happy coding!

Find whole sentence with Regex [duplicate]

This question already has answers here:
Regular expression to extract whole sentences with matching word
(4 answers)
Closed 5 years ago.
I would love to expand a selection to whole sentences. But I can't manage to produce the right regex. This is my code so far:
var re_string = "[.?!](.*?"+RegExp.quote(selector)+".*?[.?!])"
var re = new RegExp(re_string, "g");
var str = jQuery(wpccparams.selectors).text();
var m;
while ((m = re.exec(str)) !== null) {
if (m.index === re.lastIndex) {
re.lastIndex++;
}
console.log(m)
}
Example:
Selection of
"urn value to the sc" // [.?!](.*?urn value to the sc.*?[.?!])
should give me
"Unfortunately, it also echoes the return value to the screen, and fails to actually return it to the function that called the filter originally."
in this text:
".It seems that $post is only available to hooks executing at certain times. I have an “init” hook that needs to pull some data from the database using the $post->ID.So far my only workaround has been to add another filter on the_content, that uses $post to get the information I need. Unfortunately, it also echoes the return value to the screen, and fails to actually return it to the function that called the filter originally.Here is the code that extracts the data I need, but echoes and fails to return the value:"
Not working example: https://regex101.com/r/eS5jD9/2
It should also be possible to select two sentences.

[.?!]([^.?!]*?urn value to the sc.*?[.?!])
Use this..*? should not match another .?!.So use negated quantifier.See demo.
https://regex101.com/r/eS5jD9/3

CodeMirror - Using RegEx with overlay

I can't seem to find an example of anyone using RegEx matches to create an overlay in CodeMirror. The Moustaches example matching one thing at a time seems simple enough, but in the API, it says that the RegEx match returns the array of matches and I can't figure out what to do with it in the context of the structure in the moustaches example.
I have a regular expression which finds all the elements I need to highlight: I've tested it and it works.
Should I be loading up the array outside of the token function and then matching each one? Or is there a way to work with the array?
The other issue is that I want to apply different styling depending on the (biz|cms) option in the regex - one for 'biz' and another for 'cms'. There will be others but I'm trying to keep it simple.
This is as far as I have got. The comments show my confusion.
CodeMirror.defineMode("tbs", function(config, parserConfig) {
var tbsOverlay = {
token: function(stream, state) {
tbsArray = match("^<(biz|cms).([a-zA-Z0-9.]*)(\s)?(\/)?>");
if (tbsArray != null) {
for (i = 0; i < tbsArray.length; i++) {
var result = tbsArray[i];
//Do I need to stream.match each element now to get hold of each bit of text?
//Or is there some way to identify and tag all the matches?
}
}
//Obviously this bit won't work either now - even with regex
while (stream.next() != null && !stream.match("<biz.", false)) {}
return null;
}
};
return CodeMirror.overlayMode(CodeMirror.getMode(config, parserConfig.backdrop || "text/html"), tbsOverlay);
});

It returns the array as produced by RegExp.exec or String.prototype.match (see for example https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/match), so you probably don't want to iterate through it, but rather pick out specific elements the correspond to groups in your regexp (if (result[1] == "biz") ...)

Look at implementation of Code Mirror method match() and you'll see, that it processes method parameter for two types: string and RegExp.
Your constant in
stream.match("<biz.")
is of string type.
Define it in RegExp type:
tbsArray = /<biz./g
Thus, your stream will be matched with RegExp.

Best way to store JS Regex capturing groups in array?

Exactly what title asks. I'll provide some examples while explaining my question.
Test string:
var test = "#foo# #foo# bar #foo#";
Say, I want to extract all text between # (all foos but not bar).
var matches = test.match(/#(.*?)#/g);
Using .match as above, it'll store all matches but it'll simply throw away the capturing groups it seems.
var matches2 = /#(.*?)#/g.exec(test);
The .exec method apparently returns only the first result's matched string in the position 0 of the array and my only capturing group of that match in the position 1.
I've exhausted SO, Google and MDN looking for an answer to no avail.
So, my question is, is there any better way to store only the matched capturing groups than looping through it with .exec and calling array.push to store the captured groups?
My expected array for the test above should be:
[0] => (string) foo
[1] => (string) foo
[2] => (string) foo
Pure JS and jQuery answers are accepted, extra cookies if you post JSFiddle with console.log. =]

You can use .exec too like following to build an array
var arr = [],
s = "#foo# #bar# #test#",
re = /#(.*?)#/g,
item;
while (item = re.exec(s))
arr.push(item[1]);
alert(arr.join(' '));​
Working Fiddle
Found from Here
Well, it still has a loop, if you dont want a loop then I think you have to go with .replace(). In which case the code will be like
var arr = [];
var str = "#foo# #bar# #test#"
str.replace(/#(.*?)#/g, function(s, match) {
arr.push(match);
});
Check these lines from MDN DOC which explains your query about howexec updates lastIndex property I think,
If your regular expression uses the "g" flag, you can use the exec
method multiple times to find successive matches in the same string.
When you do so, the search starts at the substring of str specified by
the regular expression's lastIndex property (test will also advance
the lastIndex property).

I'm not sure if this is the answer you are looking for but you may try the following code:
var matches = [];
var test = "#foo# #foo# bar #foo#";
test.replace(/#(.*?)#/g, function (string, match) {
matches.push(match);
});
alert(JSON.stringify(matches));
Hope it helps.

data.replace(/.*?#(.*?#)/g, '$1').split(/#/)
No loops, no functions.

In case somebody arrives with a similar need to mine, I needed a matching function for a Django-style URL config handler that could pass path "arguments" to a controller. I came up with this. Naturally it wouldn't work very well if matching '$' but it wouldn't break on '$1.00'. It's a little bit more explicit than necessary. You could just return matchedGroups from the else statement and not bother with the for loop test but ;; in the middle of a loop declaration freaks people out sometimes.
var url = 'http://www.somesite.com/calendar/2014/june/6/';
var calendarMatch = /^http\:\/\/[^\/]*\/calendar\/(\d*)\/(\w*)\/(\d{1,2})\/$/;
function getMatches(str, matcher){
var matchedGroups = [];
for(var i=1,groupFail=false;groupFail===false;i++){
var group = str.replace(matcher,'$'+i);
groupFailTester = new RegExp('^\\$'+i+'$');
if(!groupFailTester.test(group) ){
matchedGroups.push(group);
}
else {
groupFail = true;
}
}
return matchedGroups;
}
console.log( getMatches(url, calendarMatch) );

Another thought, though exec is as efficient.
var s= "#foo# #foo# bar #foo#";
s= s.match(/#([^#])*#/g).join('#').replace(/^#+|#+$/g, '').split(/#+/);