Develop Reference

Double Spaces in Javascript

This code should show an alert box if there are no double spaces but it's not doing that.
var str = prompt("Enter Some Text");
var numChars = str.length;
for (var i = 0; i < numChars; i++) {
if (str.slice(i, i + 2) === " ") {
alert("No double spaces!");
break;
}
}
alert will pop out if no double spaces

You could make this a little simpler with an indexOf check:
var str = prompt("Enter Some Text");
if (str.indexOf(" ") === -1) {
alert("No double spaces!");
}

a simple regular expression can do it :
const str = prompt("Enter Some Text");
!/\s\s/.test(str) && alert('No double spaces found !');

If you want to keep that with the for approach, you should invert the logic and check whether the double whitespace occurs:
var str = prompt("Enter Some Text");
var numChars = str.length;
var doubleWhitespace = false;
for (var i = 0; i < numChars; i++) {
// get the current and next character.
var [curr, next] = [str[i], str[i + 1]];
// if both exists and current is the same as next and both the characters are spaces
if (curr && next && curr === next && curr === ' ') {
// double white space.
doubleWhitespace = true;
break;
}
}
if (doubleWhitespace) alert('There is a double space!');
else alert('NO double space');
However, there is a slightly easier solution by just using indexOf:
var str = prompt("Enter Some Text");
if (str.indexOf(' ') > -1) alert("There are double spaces!");
else alert("There are no double spaces!");

you need change this line
if (str.slice(i, i + 2) === " ") {
with
if (str.slice(i, i + 2) === " ") {

Is there a way to match every letter in a string and insert a specific letter in their place?

For example if I had the string "GCG", I'd like to insert a
"C" at every "G" match, and a "G" at every "C" match, making it GCCGGC.
So far I have the following, but it prints GCGCGC.
function pairElement(str) {
for(i = 0; i < str.length; i++) {
if(str[i] == "G") {
return str.replace(/([GC+/])/g, "GC");
} else if (str[i] == "C") {
return str.replace(/([?=CG+/])/g, "CG");
}
}
}
pairElement("GCG");
Edit: I think only the first if statement is executing and not running the else if. Are there any other methods I can use to search for different letters, not only one, and insert another letter depending on what the search for letter is?

You can convert the string into array using splitand then iterate through the array and replace each character.
Then you can use join to convert the array into string.
var string = 'GCG';
var str = string.split('').map(c => {
if(c === 'G') c = 'GC';
else if (c === 'C') c = 'CG';
return c;
}).join('');
console.log('String ' + string);
console.log('New String ' + str);

you can do
function pairElement(str) {
return str.replace(/G|C/g, e => e=='G'?'GC':'CG')
}
console.log(pairElement("GCG"));

You are not using recursion. Once it hits the return statement, the control exits. A better way would be to use regex as one of the answers suggested but if you want to just make tiny modifications in your own code, maybe try something like this.
function pairElement(str) {
var newStr= ""; // using new string to make it more readible
for(i = 0; i < str.length; i++) {
if(str[i] == "G") {
newStr = newStr + str[i] + "C";
} else if (str[i] == "C") {
newStr = newStr + str[i] + "G";
} else {
newStr = newStr + str[i]; //you didn't specify what do you want to do in this case
}
}
return newStr;
}
pairElement("GCG");

Convert sentence or camelCase word to spinal-case

I am trying to convert both sentence case and camel case to spinal case.
I am able to change camel case to by adding a space before every capital letter, but when I apply it to sentences with capital letters after spaces, I get extra spacing.
Here is my function so far :
function spinalCase(str) {
var noCamel = str.replace(/([A-Z])/g, ' $1');
var newStr = noCamel.replace(/\s|_/g, "-");
return newStr.toLowerCase();
}
spinalCase("makeThisSpinal"); //returns make-this-spinal
spinalCase("Make This Spinal"); //returns -make--this--spinal

Get lodash, specifically, https://lodash.com/docs#kebabCase.
_.kebabCase('makeThisSpinal') // make-this-spinal
_.kebabCase('Even Sentences Work') // even-sentences-work

Instead of:
var noCamel = str.replace(/([A-Z])/g, ' $1');
Try:
var noCamel = str.replace(/(\B[A-Z])/g, ' $1');

It's because you're replacing all capital letters with a space and its lowercase letter. So in your sentence, you're getting two spaces before this and spinal.
What you can do is replace all uppercase letters with "-$1" and then just remove all spaces from the string.

function spinalCase(str) {
var noCamel = str.replace(/([a-z](?=[A-Z]))/g, '$1 ')
var newStr = noCamel.replace(/\s|_/g, "-");
return newStr.toLowerCase();
}
spinalCase("makeThisSpinal"); //returns make-this-spinal
spinalCase("Make This Spinal"); //returns -make-this-spinal
Instead of str.replace(/([A-Z])/g, ' $1') for the camel case split, you should use str.replace(/([a-z](?=[A-Z]))/g, '$1 ') which will space out each word regardless of case.

Here's my solution, perhaps you will find it good reference:
function spinalCase(str) {
var newStr = str[0];
for (var j = 1; j < str.length; j++) {
// if not a letter make a dash
if (str[j].search(/\W/) !== -1 || str[j] === "_") {
newStr += "-";
}
// if a Capital letter is found
else if (str[j] === str[j].toUpperCase()) {
// and preceded by a letter or '_'
if (str[j-1].search(/\w/) !== -1 && str[j-1] !== "_") {
// insert '-' and carry on
newStr += "-";
newStr += str[j];
}
else {
newStr += str[j];
}
}
else {
newStr += str[j];
}
}
newStr = newStr.toLowerCase();
return newStr;
}

Javascript- Uppercase letters to lower case and vise versa

I am interested in making any uppercase letters lowercase and any lowercase letters uppercase.
If I have code like the below code, what should I put in the blank spaces of this if/else statement: if (string[i] == ) and the else if (string [i] == ). Here is the rest of my code:
var sentence = "Whats Up! MAKE ME uppercase or LOWERCASE";
var theString = sentence.split("")
for (var i = theString.length; i >= 0; i--) {
if (theString[i] == ) {
theString[i].toLowerCase();
}
else if (theString [i] == ) {
theString[i].toUpperCase();
}
}
var connectedSentence = theString.join("");
console.log(connectedSentence);
Have I made any other mistakes? The expected output is make me UPPERCASE OR lowercase.

You can use split, map and join to work fast on strings in javascript.
var sentence = "Whats Up! MAKE ME uppercase or LOWERCASE"
var inversed = sentence.split('').map(function(c) {
return c.toLowerCase() == c ? c.toUpperCase() : c.toLowerCase();
}).join('');

if (theString[i] == theString[i].toUpperCase()) {
theString[i]= theString[i].toLowerCase();
}
else if (theString[i] == theString[i].toLowerCase()) {
theString[i]= theString[i].toUpperCase();
}

You could simply test with RegExp;
var flipCase = function(str) {
var arr = str.split('');
var c, rgx = /[a-z]/;
str = '';
while (arr.length) {
c = arr.shift();
str += rgx.test(c) ? c.toUpperCase() : c.toLowerCase();
}
return str;
};
alert(flipCase("Hello World !"));

Is there a way I can change the contents of a variable in Camel Case to space separated words?

I have a variable which contains this:
var a = "hotelRoomNumber";
Is there a way I can create a new variable from this that contains: "Hotel Room Number" ? I need to do a split on the uppercase character but I've not seen this done anywhere before.

Well, you could use a regex, but it's simpler just to build a new string:
var a = "hotelRoomNumber";
var b = '';
if (a.length > 0) {
b += a[0].toUpperCase();
for (var i = 1; i != a.length; ++i) {
b += a[i] === a[i].toUpperCase() ? ' ' + a[i] : a[i];
}
}
// Now b === "Hotel Room Number"

var str = "mySampleString";
str = str.replace(/([A-Z])/g, ' $1').replace(/^./, function(str){ return str.toUpperCase(); });
http://jsfiddle.net/PrashantJ/zX8RL/1/

I have made a function here:
http://jsfiddle.net/wZf6Z/2/
function camelToSpaceSeperated(string)
{
var char, i, spaceSeperated = '';
// iterate through each char
for (i = 0; i < string.length; i++) {
char = string.charAt(i); // current char
if (i > 0 && char === char.toUpperCase()) { // if is uppercase
spaceSeperated += ' ' + char;
} else {
spaceSeperated += char;
}
}
// Make the first char uppercase
spaceSeperated = spaceSeperated.charAt(0).toUpperCase() + spaceSeperated.substr(1);
return spaceSeperated;
}
The general idea is to iterate through each char in the string, check if the current char is already uppercased, if so then prepend a space to it.