Develop Reference

Is there a better way to chain the String#replace method?

I understand that regex is a possibility, but I'd like to edit a lot of things at once. Minimalizing chaining. It just doesn't look to great in code.
for example,
Let's say the alphabet is jumbled up.
A would be E
B would be H
E would be D
How would I change ABE into EHD using a minimal amount of functions?
To be crystal clear, I have an object with this jumbled up alphabet.
TL;DR:
Best way to bulk-update letters in a string to their assigned counterparts?

You could write some logic where you would split the string into an array of characters and then compare the separate values using map() and replace when needed. Then join the array back to a string.
const original = "ABE";
const splitted = original.split("");
const replaced = splitted.map((letter) => {
if(letter === "A") return "E"
if(letter === "B") return "H"
if(letter === "E") return "D"
return letter
});
console.log(replaced.join(""));

The easiest would be to use a regular expression but also pair it with a replacer function:
const substitutions = {
"A": "E",
"B": "H",
"E": "D"
};
function transform(input) {
return input.replace(/./g, char => {
const sub = substitutions[char] ?? char;
return sub;
});
}
console.log(transform("HELLO WORLD!"));
console.log(transform("BEAUTIFUL!"));
console.log(transform("BOATS ARE EXCELLENT 👍"));
The regex /./g simply matches every single character and the replacer function then checks if it exists in substitutions and returns that. Or if it doesn't exist, it falls back to the same character thanks to the nullish coalescing operator (??).
This requires you to specify lowercase and uppercase characters explicitly in substitutions.
const substitutions = {
"a": "e",
"A": "E",
"b": "h",
"B": "H",
"e": "d",
"E": "D"
};
function transform(input) {
return input.replace(/./g, char => {
const sub = substitutions[char] ?? char;
return sub;
});
}
console.log(transform("Hello world!"));
console.log(transform("Beautiful!"));
console.log(transform("Boats Are Excellent 👍"));
If you always want the replacement to match the case (a -> e and A -> E) and do not want the extra entries in substitutions, then you can can check the case of the character and transform the replacement:
const substitutions = {
"A": "E",
"B": "H",
"E": "D"
};
function transform(input) {
return input.replace(/./g, char => {
const upperChar = char.toLocaleUpperCase();
if (!(upperChar in substitutions))
return char;
const isUpper = char === upperChar;
const sub = substitutions[upperChar];
if (isUpper)
return sub.toLocaleUpperCase();
return sub.toLocaleLowerCase();
});
}
console.log(transform("Hello world!"));
console.log(transform("Beautiful!"));
console.log(transform("Boats Are Excellent 👍"));

How to use str.replace with many find/replace pairs in JavaScript

I need a function in JavaScript that takes one string as input, replaces many substrings with their corresponding values, then returns the result. For example:
function findreplace(inputStr) {
const values = {"a": "A",
"B": "x",
"c": "C"};
// In this example, if inputStr is "abc", then outputStr should be "AbC".
return outputStr
}
I know how to individually find and replace, but I was wondering if there was an easy way to do this with many pairs of (case-sensitive) values at once.
Thank you!

Just iterate over values with the help of Object.entries(values):
function findreplace(inputStr) {
const values = {
"a": "A",
"B": "x",
"c": "C"
};
for (const [search, replace] of Object.entries(values)) {
inputStr = inputStr.replace(search, replace);
}
return inputStr;
}
console.log(findreplace("abc"));

You can join keys to build a regex and then replace accordingly
function findreplace(inputStr) {
let values = { "a": "A", "B": "x", "c": "C" };
let regex = new RegExp("\\b" + Object.keys(values).join('|') + "\\b", 'g')
return inputStr.replace(regex, (m) => values[m] )
}
console.log(findreplace('aBc'))
console.log(findreplace('AbC'))
console.log(findreplace('ABC'))

Get values from Key/Value variable in javascript

Please consider this scenario:
I have a Key/Value variable like this:
var dict = {"78": "X",
"12": "G",
"18": "R",
"67": "U",
"68": "O",
"30": "P"}
I have a string that I want to check if there is a letter of my variable exist in my string. How I can do this?

Collect object key values and use them to create a regular expression. Then use .test(yourString):
var myStr = "Group";
new RegExp(Object.keys(dict).map(function (c) { return dict[c]; }).join("|"))
.test(myStr); // true
Another way is simply iterating the object:
var found = false;
for (var k in dict) {
if (myStr.indexOf(dict[k]) !== -1) {
found = true;
break;
}
}
if (found) {
// letter found
}

One possible approach:
var contains = Object.keys(dict).some(function(key) {
return someStr.indexOf(dict[key]) !== -1;
});
In other words, iterate over the collection, at each step checking whether or not the tested character present in your string (someStr). If it is, stops the iteration immediately (that's how Array.prototype.some works).
Another approach is building a character class regex, then using it against the string:
var pattern = RegExp('[' + Object.keys(dict).map(function(k) {
return dict[k];
}).join('') + ']');
var contains = pattern.test(someStr);
The second approach is slightly better if the tested strings usually do contain the characters from dict. It's also quite easy to augment this solution into case-insensitive search - just add 'i' string as a second param of RegExp call.
The caveat is that you'll have to escape the characters that will be considered meta within a string passed into RegExp constructor (backslash, for example). If there are no such characters in the dictionary, it's not a problem, though.

It can be done using the following:
str = "test";
isExists = false;
for(var key in dict){
isExists = str.indexOf(dict[key]) !== -1;
if(isExists)
break;
};
console.log(isExists);

How to split words using javascript

This might be a simple question but, how do i split words... for example
a = "even, test"
I have used .split to seperate the text with space.
so the result came is like
a = "even,"
b = "test"
But, how do I remove the 'comma' here?
But in some conditions it might get "even test" and in some conditions i might get "even, test". All are dynamic, so how do i check it for both?
Thanks

Firstly, the split() function is not jQuery - it is pure Javascript.
Did you try doing split with a comma and a space? That would have worked just fine in your case:
var result = input.split(', ');
For more complex splits, you can use regular expression pattern matching to allow multiple commas or spaces between the two fields:
var result = input.split(/[, ]+/);
but you probably don't need to go that far in your case.

I think is better to use something like this:
text.match(/[a-z'\-]+/gi);
Example:
var e=function()
{
var r=document.getElementById('r');
var x=document.getElementById('t').value.match(/[a-z'\-]+/gi);
for(var i=0;i<x.length;i++)
{
var li=document.createElement('li');
li.innerText=x[i];
r.appendChild(li);
}
}
<div style="float:right;width:18%">
<ol id="r" style="display:block;width:auto;border:1px inner;overflow:scroll;height:8em;max-height:10em;"></ol>
<button onclick="e()">Extract words!</button>
</div>
<textarea id="t" style="width:70%;height:12em">even, test; spider-man
But saying o'er what I have said before:
My child is yet a stranger in the world;
She hath not seen the change of fourteen years,
Let two more summers wither in their pride,
Ere we may think her ripe to be a bride.
—Shakespeare, William. The Tragedy of Romeo and Juliet</textarea>

I found a list of word separators in Sublime Text default settings.
Here's how to split with it, with some Unicode support (the defined separators are not Unicode though):
{ // word_separators: ./\()"'-,;<>~!##$%^&*|+=[]{}`~?: (32)
function splitByWords(str = '', limit = undefined) {
return str.split(/[-./\\()"',;<>~!##$%^&*|+=[\]{}`~?:]/u, limit)
}
function reverseString(str) {
let newString = ''
for (let i = str.length - 1; i >= 0; i--)
newString += str[i]
return newString
}
const str = '123.x/x\\x(x)x"x\'x-x:x,789;x<x>x~x!x#x#x$x%x^x&x*x|x+x=x[x]x{x}x`x~x?456'
console.log(splitByWords(str)) // (33) ["123", "x", "x", "x", "x", "x", "x", "x", "x", "x", "789", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "456"]
console.log(splitByWords(str, 1)) // ["123"]
console.log(splitByWords(reverseString(str), 1)) // ["654"]
}
For some reason the - has to be at the beginning, and the : at the end.
Edit: you might want to add \s (after the -) to count whitespace as separator

Just use this code:
var a = "even, test";
var words = a.split(", ");

a.split(',')
or
var re = /\s*,\s*/
var newA = a.split(re);

I think you could do it like this:
var a= 'even,'
var newA = a.slice(0, -1)
This will remove the last char from a given string.
And to check if the string contains a comma, I would do the following:
if (a.indexOf(",") >= 0){
//contains a comma
} else {
//no comma
}
I am a javascript beginner, so this probably is not the best way to do it, but nevertheless it works.

Hej Harry
if the comma is the separator you can call split with the comma
Ex:
var newColls = myString.split(",");
and not split with space.
GL

Javascript Match and RegExp Issue -- Strange Behavior

I have been trying to use a simple jQuery operation to dynamically match and store all anchor tags and their texts on the page. But I have found a weird behavior. When you are using match() or exec(), if you designate the needle as a separate RegExp object or a pattern variable, then your query matches only one instance among dozens in the haystack.
And if you designate the pattern like this
match(/needle/gi)
then it matches every instance of the needle.
Here is my code.
You can even fire up Firebug and try this code right here on this page.
var a = {'text':'','parent':[]};
$("a").each(function(i,n) {
var module = $.trim($(n).text());
a.text += module.toLowerCase() + ',' + i + ',';
a.parent.push($(n).parent().parent());
});
var stringLowerCase = 'b';
var regex = new RegExp(stringLowerCase, "gi");
//console.log(a.text);
console.log("regex 1: ", regex.exec(a.text));
var regex2 = "/" + stringLowerCase + "/";
console.log("regex 2: ", a.text.match(regex2));
console.log("regex 3: ", a.text.match(/b/gi));
For me it is returning:
regex 1: ["b"]
regex 2: null
regex 3: ["b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b", "b"]
Can anyone explain the root of this behavior?
EDIT: I forgot to mention that for regex1, it doesn't make any difference whether you add the flags "gi" for global and case insensitive matching. It still returns only one match.
EDIT2: SOlved my own problem. I still don't know why one regex1 matches only one instance, but I managed to match all instances using the match() and the regex1.
So..this matches all and dynamically!
var regex = new RegExp(stringLowerCase, "gi");
console.log("regex 2: ", a.text.match(regex));

This is not unusual behaviour at all. In regex 1 you are only checking for 1 instance of it where in regex 3 you have told it to return all instances of the item by using the /gi argument.
In Regex 2 you are assuming that "/b/" === /b/ when it doesn't. "/b/" !== /b/. "/b/" is a string that is searching so if you string has "/b/" in it then it will return while /b/ means that it needs to search between the slashes so you could have "abc" and it will return "b"
I hope that helps.
EDIT:
Looking into it a little bit more, the exec methods returns the first match that it finds rather than all the matches that it finds.
EDIT:
var myRe = /ab*/g;
var str = "abbcdefabh";
var myArray;
while ((myArray = myRe.exec(str)) != null)
{
var msg = "Found " + myArray[0] + ". ";
msg += "Next match starts at " + myRe.lastIndex;
console.log(msg);
}
Having a look at it again it definitely does return the first instance that it finds. If you looped through it then would return more.
Why it does this? I have no idea...my JavaScript Kung Fu clearly isnt strong enough to answer that part

The reason regex 2 is returning null is that you're passing "/b/" as the pattern parameter, while "b" is actually the only thing that is actually part of the pattern. The slashes are shorthand for regex, just as [ ] is for array. So if you were to replace that to just new regex("b"), you'd get one match, but only one, since you're omitting the "global+ignorecase" flags in that example. To get the same results for #2 and #3, modify accordingly:
var regex2 = stringLowerCase;
console.log("regex 2: ", a.text.match(regex2, "gi"));
console.log("regex 3: ", a.text.match(/b/gi));

regex2 is a string, not a RegExp, I had trouble too using this kind of syntax, tho i'm not really sure of the behavior.
Edit : Remebered : for regex2, JS looks for "/b/" as a needle, not "b".