I have working code for a simple word flipper:
var strFlip = function(str) {
return str.split(" ").map(function(word) {
return word.split("").reverse().join("");
}).join(" ");
};
console.log(strFlip("This is designed to swap the letter order of each word in the string"));
// "sihT si dengised ot paws eht rettel redro fo hcae drow ni eht gnirts"
I want to add an if/else to allow this code to now identify if each word in a string is a palindrome (spelled the same forward and backward ex: hannah).
So I tried continuing the .map() logic with:
var strFlip = function(str) {
return str.split(" ").map(function(word) {
return word.split("").reverse().join("");
}).join(" ").toLowerCase().map(function(test) {
if (test.split(" ") === word){
return true;
}else{
return false;
}
}
);
};
console.log(strFlip("Hannah loves her racecar"));
BUT.... unsurprisingly, it returns an error essentially stating that the long linked collection of functions before the if section is not itself a function:
TypeError: str.split(...).map(...).join(...).toLowerCase(...).map is not a function
I was also getting lost trying to match all of the curly braces, but I think I got them all.
So, is it possible to add the if/else within?
.join(" ").toLowerCase() returns a string, not an array. The error is stating that 'some string'.map is not a function because it's undefined.
If what you want is an array that indicates whether a word at an index is a palindrome then...
var sentence = 'Eve drives a racecar',
words = sentence.split(" ").map(function(word) {
var isPalindrome = word.length > 1 && (word.toLowerCase() === word.toLowerCase().split("").reverse().join(""));
return { text: word, isPalindrome: isPalindrome };
});
alert(JSON.stringify(words));
Related
I have written a code that removes all consonants before a vowel from a string and replaces it with an 'r' and in the case, the string starts with a vowel it should return the word without doing anything to it. Now, I want to add two things I came up with to it but unfortunately, I have not been able to:
1. When the string input is all consonants then it should do nothing and just return the string.
2. If user types in space like so ' ' then it should be trimmed.
How do I place this logic in the code below without affecting what is already working?
const scoobyDoo = str => {
if(typeof str !== 'string'){
return 'This function accepts strings only';
}
let newStr = str.toLowerCase().split('');
let arrWord = newStr.length;
let regex = /[aeiou]/gi;
if (newStr[0].match(regex)){
let nothing = newStr.join('');
return nothing;
}
else {
for (let i = 0; i < arrWord; i++){
let vowelIndex = newStr.indexOf(str.match(regex)[i].toLowerCase());
newStr.splice(0, vowelIndex, 'r');
return newStr.join('');
}
}
}
console.log(scoobyDoo('scooby'));//works as expected returns 'rooby'
console.log(scoobyDoo('ethane'));//works as expected returns 'ethane'
console.log(scoobyDoo('why'));// should return 'why'
console.log(scoobyDoo(' '));// should return trimmed space and a
text telling the user only spaces were entered.
I realise this doesn't really answer your question, but your existing logic is very complicated and you could achieve the same result with String.trim, .toLowerCase and .replace:
console.log('scooby'.trim().toLowerCase().replace(/^(?=.*?[aeiou])[^aeiou]+/, 'r'))
rooby
console.log('ethane'.trim().toLowerCase().replace(/^(?=.*?[aeiou])[^aeiou]+/, 'r'))
ethane
console.log('why'.trim().toLowerCase().replace(/^(?=.*?[aeiou])[^aeiou]+/, 'r'))
why
console.log('*' + ' '.trim().toLowerCase().replace(/^(?=.*?[aeiou])[^aeiou]+/, 'r') + '*')
**
The regexp uses a positive lookahead to ensure that there is a vowel in the string, and if so replaces all leading consonants with an r.
To do something more in line with your existing function, you could try this. It still makes extensive use of regex functions though.
const scoobyDoo = str => {
if(typeof str !== 'string'){
return 'This function accepts strings only';
}
// is it a blank string?
if (str.match(/^\s+$/)) {
return '';
}
// does it start with a vowel? if so, nothing to do
if (str.match(/^[aeiou]/i)) {
return str;
}
// does it only contain consonants?
if (!str.match(/[aeiou]/i)) {
return str;
}
// must not start with a vowel but still include one
return str.replace(/^[^aeiou]+/i, 'r');
}
When I run the snippet below in JSbin it says that capitalize won't work because the property is undefined. I looked at the documentation and it mentioned the use of the word 'this' but I am not quite sure if that applies here since the string value passed in is correct (console logged it to confirm). Why is the capitalize method not apple to work off the map value?
class bookTitle {
constructor(title) {
this.title = title; // this creates the object ONCE, see top of jasmine file for explanation
}
get title() {
return this._title; // retrieves the title string
}
set title(title) {
this._title = this.titleCreator(title); // calls the method and sets title, see top of jasmine file for explanation
}
titleCreator(string) {
if (string == null){
return string; // catches first error
}
// Note that this isn't meant to be a fully fledged title creator, just designed to pass these specific tests
var littleWords = ['and', 'do', 'the', 'a', 'an', 'in', 'of']; // These are the words that we don't want to capitalize
var modifiedString = string
.split(' ') // Splits string into array of words, basically breaks up the sentence
.map(function(word,index) {
if (index == 0) {
return this.capitalize(word); // capitalize the first word of the string
} else if (littleWords.indexOf(word) == -1) {
return this.capitalize(word); // capitalize any words that are not little, the -1 is returned by indexOf if it can't find the word in the array
} else if (littleWords.indexOf(word) >= 0) {
return word; // do not capitalize as this word is in the list of littleWords
}
})
.join(' '); // Joins every element of an array into a string with a space inbetween each value. Basically you created a sentence from an array of words
return modifiedString;
}
capitalize(word) {
return word.charAt(0).toUpperCase() + word.slice(1);
// This function just capitalizes the word given to it
}
}
let bookTitles = new bookTitle();
bookTitles.title = 'inferno';
console.log(bookTitles.title); // The goal is to output Inferno
The problem is that this within your map refers to the function you're passing to map. Use an arrow function (word, index) => { ... } instead and this should fall through to the parent class.
var modifiedString = string
.split(' ') // Splits string into array of words, basically breaks up the sentence
.map((word,index) => { // <-- ARROW FUNCTION
if (index == 0) {
return this.capitalize(word); // capitalize the first word of the string
} else if (littleWords.indexOf(word) == -1) {
return this.capitalize(word); // capitalize any words that are not little, the -1 is returned by indexOf if it can't find the word in the array
} else if (littleWords.indexOf(word) >= 0) {
return word; // do not capitalize as this word is in the list of littleWords
}
})
.join(' ');
I'm aware of the CSS attribute text-transform: capitalize but can anyone help me with replicating this using Javascript?
I would like to pass an argument to my function which will return the string with the first letter of each word capitalized.
I've got this far but I'm stuck trying to break my array of strings in to chunks:
function upper(x){
x = x.split(" ");
// this function should return chunks but when called I'm getting undefined
Array.prototype.chunk = function ( n ) {
return [ this.slice( 0, n ) ].concat( this.slice(n).chunk(n) );
};
x = x.chunk;
}
upper("chimpanzees like cigars")
after the chunk I'm guessing I need to again split each chunk in to the first character and the remaining characters, use .toUpperCase() on the first character, join it back up with the remaining and then join up the chunks again in to a string?
Is there a simpler method for doing this?
I came up with a solution for both a single word and also for an array of words. It will also ensure that all other letters are lowercase for good measure. I used the Airbnb style guide as well. I hope this helps!
const mixedArr = ['foo', 'bAr', 'Bas', 'toTESmaGoaTs'];
const word = 'taMpa';
function capitalizeOne(str) {
return str.charAt(0).toUpperCase().concat(str.slice(1).toLowerCase());
}
function capitalizeMany(args) {
return args.map(e => {
return e.charAt(0).toUpperCase().concat(e.slice(1).toLowerCase());
});
};
const cappedSingle = capitalizeOne(word);
const cappedMany = capitalizeMany(mixedArr);
console.log(cappedSingle);
console.log(cappedMany);
The map function is perfect for this.
w[0].toUpperCase() : Use this to capitalize the first letter of each word
w.slice(1): Return the string from the second character on
EDGE Case
If the user doesn't enter a string, the map function will not work and an error will be raised. This can be guarded against by checking if the user actually entered something.
var userInput = prompt("Enter a string");
var capitalizedString = userInput == "" ? "Invalid String" :
userInput.split(/\s+/).map(w => w[0].toUpperCase() + w.slice(1)).join(' ');
console.log(capitalizedString);
You can use the following solution which doesn't use regex.
function capitalize(str=''){
return str.trim().split('')
.map((char,i) => i === 0 ? char.toUpperCase() : char )
.reduce((final,char)=> final += char, '' )
}
capitalize(' hello') // Hello
"abcd efg ijk lmn".replace(/\b(.)/g, (m => m.toUpperCase())) // Abcd Efg Ijk Lmn
You may want to try a regex approach:
function upperCaseFirst(value) {
var regex = /(\b[a-z](?!\s))/g;
return value ? value.replace(regex, function (v) {
return v.toUpperCase();
}) : '';
}
This will grab the first letter of every word on a sentence and capitalize it, but if you only want the first letter of the sentence, you can just remove the g modifier at the end of the regex declaration.
or you could just iterate the string and do the job:
function capitalize(lowerStr){
var result = "";
var isSpacePrevious = false;
for (var i=0; i<lowerStr.length; i++){
if (i== 0 || isSpacePrevious){
result += lowerStr[i].toUpperCase();
isSpacePrevious = false;
continue;
}
if (lowerStr[i] === ' '){
isSpacePrevious = true;
}
result += lowerStr[i];
}
return result;
}
This is a solution to a toy problem in Javascript. The job was to find a Palindrome(word that you can read the same back and forth, like "radar", "rotor") in a string with words separated by spaces or return an empty string if no word fits the requirement. i understand everything but i don´t know how they use the reduce method to find the word, especially the syntax " ? word : prevWord"
Could somebody explain??
function reverseString(str) {
return str.split('').reverse().join('');
}
function isPalindrome(str) {
return str === reverseString(str);
}
function getWords(str) {
return str.split(' ');
}
function findPalindrome(str) {
var words = getWords(str);
return words.reduce(function(prevWord, word) {
return isPalindrome(word) ? word : prevWord;
}, '');
}
As you can see if i use the last function
findPalindrome("this is a very good rotor");
It will return
"rotor"
I am writing a function which takes string as an argument. Then if the string begins with capital letter then return true otherwise return false. But my current function only works for one word string which I want it to work for both one word and a whole sentence. How can I improve my code to achieve this? Secondly, it should not work when numbers are passed inside sentence. How can I do this?
Here is my code
function takeString (str) {
var regex = /^[A-Za-z]+$/;
if (str.match(regex)) {
if (str.charAt(0) === str.toUpperCase().charAt(0)) {
alert('true');
return true;
} else {
alert('false');
return false;
}
} else {
alert('Only letters please.');
}
}
takeString('This is'); // shows Only letters please which is wrong. this should work
takeString('String); // returns true which right
takeString('string'); // returns false which is right
takeString('This is 12312321'); // shows only letters please which is right bcoz it has digits
takeString('12312312'); // show Only letters please which is right.
Spaces aren't letters. You have to add them into your character set:
> 'This is a string'.match(/^[A-Za-z]+$/);
null
> 'This is a string'.match(/^[A-Za-z\s]+$/);
["This is a string"]
\s matches all whitespace, so if you don't want to match tabs, replace \s with a space.
Here's a slightly more condensed version of your code:
function takeString(str) {
return str.match(/^[A-Z][A-Za-z ]*$/);
}
along with the regex advice given by Blender, you'll want to also do the following (in order to satisfy the need to check each word ... assuming words are space or tab separated only:
use the split function to break the string into words ( var mywords = str.split(/\s+/) )
iterate over mywords array returned by split, checking each array element against the regex
return an error if the regex doesnt match
return success if you match every word
takeString (str) {
var mywords = str.split(/\s+/);
for (i = 0; i < mywords.length; i++) {
if (str.match(/^[A-Z][A-Za-z]*$/) != true) {
return false;
}
}
return true;
}
(someone needs to check my js ... )