Develop Reference

Make a camel-case function using a for loop in Javascript

I am brand new to Javascript and trying to figure out how to camel-case any string by using a for loop. This is what I have so far.
function camelCase(str) {
var splitStr = "";
var result = "";
splitStr = str.split(" ");
for(var i = 0; i < splitStr.length; i++){
result += splitStr[i][0].toUpperCase() +
splitStr[i].slice(1);
}
return result;
}
console.log(camelCase("hello there people"));
it returns "HelloTherePeople" - How do you I make the very first index of splitStr (splitStr[0][0]) be excluded from toUpperCase, but still included in the beginning of the string?

What is your delimiter? This method assumes an underscore _. Change it to a space if you want a space. Or make it a variable you can pass to camelize.
if( !String.prototype.camelize )
String.prototype.camelize = function(){
return this.replace(/_+(.)?/g, function(match, chr) {
return chr ? chr.toUpperCase() : '';
});
}
"a_new_string".camelize()
//"aNewString"
The regex /_+(.)?/g/ says find 1 or more _ characters followed by any character ., the (.) creates a capturing group, so you are able to get that one character. It's passed to the function as the second paramater chr. The ? means not greedy so it will stop at the next _. The g means globally, pretty much means find all matches.
String.prototype.replace reference

change return like this:
return result[0].toLowerCase()+result.substr(1);

You can do a check inside the loop to see if you are on the first index.
function camelCase(str) {
//splitStr will be an array
var splitStr = [];
var result = "";
splitStr = str.split(" ");
//Capitalize first letter of words starting from the second one
for(var i = 0; i < splitStr.length; i++){
//first word
if (i===0) {
//Good practice to lowercase the first letter regardless of input
result += splitStr[i][0].toLowerCase() + splitStr[i].slice(1);
}
else {
//rest can proceed as before
result += splitStr[i][0].toUpperCase() +
splitStr[i].slice(1);
}
}
return result;
}
console.log(camelCase("hello there people"));
Alternatively, the loop can even start on the second index. However, you will have to check if the length of splitStr before running a loop from the second index

Changing individual characters in a string does not work in a loop [duplicate]

This question already has answers here:
The .replace() method does change the string in place [duplicate]
(3 answers)
Closed 4 years ago.
So, I'm working on some exercise questions. My code seems to be working fine up until I decide to loop through the string to replace any instance of a period with nothing. For some reason, the loop doesn't work. I imagine it has something to do with not calling it somehow, but I'm not sure how to call the loop. I thought that loops automatically overwrote what they are looping through. Here is the exercise and my incomplete solution:
Write a JavaScript function to parameterize a string.
function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var split_string = lowercase_string.split(" ");
var joined_string = split_string.join("-");
for (i = 0; i < joined_string.length; i++) {
if (joined_string[i] === ".") {
joined_string[i] === "";
}
}
return joined_string;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));
The answer should be robin-singh-from-usa without the period, but it keeps coming out as robin-singh-from-usa. with the period.

The other answers are not taking into account that strings in JavaScript are immutable. You can not change individual characters in a string. You build a new string.
In JavaScript, strings are immutable. Trying to change the characters in a string does not work:
function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var split_string = lowercase_string.split(" ");
var joined_string = split_string.join("-");
for (i = 0; i < joined_string.length; i++) {
if (joined_string[i] === ".") {
joined_string[i] = "";
}
}
return joined_string;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA.")); //This will not work:
You can build a new string using your for loop to individually add each character that is not a . to the newString:
function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var split_string = lowercase_string.split(" ");
var joined_string = split_string.join("-");
var newString = '';
for (i = 0; i < joined_string.length; i++) {
if (joined_string[i] !== ".") {
newString += joined_string[i];
} //We are replacing '.' with nothing, '', so no need for an else
}
return newString;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));
Regular Expressions
This would, however, normally be done with Regular Expressions, specifically the .replace() method:
function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var newString = lowercase_string.replace(/ /g,'-'); //Replace all spaces with '-'.
var newString = newString.replace(/\./g,''); //Replace all '.' with nothing. The '.'
// has to be quoted with \. as it
// has special meaning in a RegExp.
return newString;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));
Which can be done all in one statement:
function string_parameterize(string) {
return string.toLowerCase().replace(/ /g,'-').replace(/\./g,'');
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));

You can put in a [...]+ every character you don't want have in the output.
var res = string.toLowerCase().replace(/[%\(\)\.\s]+/g, "-").replace(/-$/, "");
// ^ ^ ^ ^
// Here the characters you don't want to have in the output
+ means matched one ore more times. Replace the matched characters with -.
Then remove last - with -$.
In total
function string_parameterize(string) {
var res = string.toLowerCase().replace(/[%\(\)\.\s]+/g, "-").replace(/-$/, "");
return res;
}
console.log(string_parameterize("Это тест")); // A russian sentence
console.log(string_parameterize("Robin Singh%%() from USA. "));
console.log(string_parameterize("Robin ...Singh from USA....."));
console.log(string_parameterize("Robin Singh from USA "));
console.log(string_parameterize("Robin Singh from USA"));
Info about regular expression.

function string_parameterize(string) {
var lowercase_string = string.toLowerCase();
var split_string = lowercase_string.split(" ");
var joined_string = split_string.join("-");
joined_string = joined_string.replace(".", "");
return joined_string;
}
//Test Data :
console.log(string_parameterize("Robin Singh from USA."));
This is working in IE.

function string_parameterize(str){
return str.toLowerCase().replace(".", "").split(" ").join("-");
}
console.log(string_parameterize("Robin Singh from USA."));
//will result in: robin-singh-from-usa
Your code is not working because in if condition you are checking for joined_string[i]==="." to be equal to '.' and actually it is equal to 'USA.'. That is why this if condition never met with and return the '.' in the final result:
if (joined_string[i]===".") {
joined_string[i]==="";
}

You're checking the value of joined_string[i], rather than assigning it.
joined_string[i] = "";
not
joined_string[i] === "";

Change:
if (joined_string[i]===".") {
joined_string[i]==="";
}
to
if (joined_string[i]===".") {
joined_string[i]="";
}

Javascript - Find an replace a part of a string with value from an array

I have an string, but at certain points in the string it has dynamic values.
I want to find those points in the string and replace them with values from an array.
Let's say I have:
var array = ['string', 'value'];
var string = 'This is a {1}, and this is a {2}.';
Now I need to figure out a way to replace {1}, with the value of the first index in the array and replace {2} with the value of the second index of the array.
So the string would like this:
This is a string, and this is a value.
This seems so simple, but I am breaking my head on this. I can't find a way to do this easily.

You can use replace with a regular expression and a function:
string.replace(/{(\d+)}/g, function(match, n) {
return array[n-1];
});
You can also check n < 1 || n > array.length to provide a fallback value in case the number is out of bounds.
Alternatively, the new ES6 way is using tagged template strings
function tag(strings, ...values) {
var parts = [];
for(var i=0; i<strings.length; ++i)
parts.push(strings[i], array[values[i]-1]);
return parts.join('');
}
tag`This is a ${1}, and this is a ${2}.`

like this
string.replace(/\{(\d+)\}/g, function(m, n){
return array[n-1]
})

You can use Array.prototype.reduce:
var StringHelper = {
format: function(format, args) {
return args.reduce(function(result, currentReplace, currentReplaceIndex) {
result = result.replace("{" + (currentReplaceIndex + 1) + "}", args[currentReplaceIndex]);
return result;
}, format);
}
};
var sourceString = "My name is {1} and I'm {2} years old";
var replaceItems = ["Matías", "31"];
var parsedString = StringHelper.format(sourceString, replaceItems);
alert(parsedString);
It's a good alternative to regular expressions, and I'm not absolutely sure if I did a jsPerf test in the right way, but it shows that this approach outperforms the regular expression one.

Please explain to me prototypes in javascript using the code below

I am trying to use the prototype method of writing functions that can be implemented by strings to capitalise every first letter of every word. I would like to call this function like,
var str = "Example of a string";
str.toJadenCase();
This is the function I am trying to write:
String.prototype.toJadenCase = function () {
//split the statement into each word
if (String.prototype.length !== 0)
{
var eachWord = String.prototype.split(" ");
var n = eachWord.length;
if(n !== 0)
{
//loop through the array of words
for(var i = 0; i < eachWord.length; i++){
//for each loop, split the word into individual characters
var charArray = eachWord[i].split("");
//capitalise the first element of character array
charArray[0] = charArray[0].toUpperCase();
//join all elements in character array to string
eachWord[i] = charArray.join("");
}
//join all the words to form the statement
String.prototype = eachWord.join(" ");
return String.prototype;
}
}
};
I had written it this way before:
var capitaliseInitial = function(sampleText){
var textString = sampleText;
//split the statement into each word
var eachWord = textString.split(" ");
//loop through the array of words
for(var i = 0; i < eachWord.length; i++){
//for each loop, split the word into individual characters
var charArray = eachWord[i].split("");
//capitalise the first element of character array
charArray[0] = charArray[0].toUpperCase();
//join all elements in character array to string
eachWord[i] = charArray.join("");
}
//join all the words to form the statement
textString = eachWord.join(" ");
return textString;
}

I would like to call this function like,
var str = "Example of a string";
str.toJadenCase();
You can't, strings are immutable. You would have to call it like this:
str = str.toJadenCase();
In your function, you're using String.prototype incorrectly. String.prototype is the object containing the various String-specific methods. It's assigned as the underlying prototype of all strings.
Where you're using String.prototype, you should be using this, and instead of trying to assign to it (this = ... is invalid), return the result.
The simple way to do what you're doing is to:
Split the string into an array of words, as you have
Loop through that array either building up a new string with the capitalized words via +=, or building a new array with the capitalized words and then doing Array#join at the end to put it back together.
Return the string you built
Something like this:
String.prototype.toJadenCase = function() {
var result = this;
//split the statement into each word
if (this.length !== 0) {
result = this.split(" ").map(function(word) {
return word.substring(0, 1).toUpperCase() + word.substring(1);
}).join(" ");
}
return result;
};
snippet.log("this is a test".toJadenCase());
snippet.log("oneword".toJadenCase());
snippet.log("blank: " + ("".toJadenCase()));
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>
Note I've done away with the check if the array of words' length isn't 0: It can't be 0 if you've pre-checked the length as you have.

use RegExp and php like naming
str.ucwords()
String.prototype.ucwords = function() {
return this.replace(/\b\S/g,function(c){
return c.toUpperCase()
}
}

Here's how I did mine.
Split the string into an array of words, as you have
Loop through that array either building up a new string with the capitalized words via +=, or building a new array with the capitalized words and then doing Array#join at the end to put it back together.
Return the string you built
String.prototype.toJadenCase = function () { return this.split(" ").map(function(word){ return word.charAt(0).toUpperCase() + word.slice(1); }).join(" "); }

This look like one of the Code Wars Katas - this was my solution -
String.prototype.toJadenCase = function () {
// assign 'this' keyword to a variable and split String into an array
var result = this.split(" ");
/* loop through the array changing first character of each item to
uppercase & adding it to the remaining letters in each item */
for(i = 0; i < result.length; i++) {
result[i] = result[i].charAt(0).toUpperCase() + result[i].substring(1);
}
//finally return items joined back together in a string
return result.join(' ');
};

another way to do this would be like:
String.prototype.toJadenCase = function() {
return this
.split(" ")
.map(i => i.replace(i[0], i[0].toUpperCase()))
.join(" ");
};

JavaScript function - Looping through a string, styling individual characters

I am trying to pass a number string through a function that iterates through each character, wrapping each in a element if it is or is not a number.
var str = "$6,117,766.69";
var nonNumber = "$,.";
for (var i = 0; i < str.length; i++) {
if (nonNumber.contains(str[i])) {
$('body').append("<span class = 'thecolorYellow'>"+str[i]+"</span>");
} else {
$('body').append("<span class = 'thecolorBlue'>"+str[i]+"</span>");
}
}
My question is this: How can I make this a function that returns this as a string instead of modifying the DOM? And second, how could I adapt this function to make sure that characters outside of 0-9 and the three non-numerics are omitted from the final string?

I'd suggest you use replace to generate the markup, then you can append it all at once:
var html = str.replace(/./g, function(match) {
var clas = isNaN(match) ? 'yellow' : 'blue'
return '<span class="'+ clas +'">'+ match +'</span>'
})
$('body').append(html)

function getAmountAsNumber(dollarAmount)
{
return dollarAmount.replace(/\D/g,'');
}
The above function will return just the digits 0-9 from your input string and will also make sure that all your non-numeric characters are ommitted.