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Find same position in two strings that are slightly different

I have two strings where the first is a master string and the second is a slave string. They both contain similar values except that the slave will have characters added or removed.
I need to find the character offset from the master string in the slave string for each character of the master string.
I'm currently using a percentage as the algorithm for finding the similar offset in the slave string.
For example;
const master = 'The chicken is blue, but not really a chicken';
const slave = 'This large bird is blue, but is really a dog';
function slaveOffset(m, offset, s): number {
return Math.floor(s.length * (offset / m.length));
}
console.log(slaveOffset(master, 15, slave)); // prints 12
When translating the position 15 from the master (which reads "The chicken is ") the slave position is calculated as 12. Which reads as "This large b" because using percentage is not at all accurate (doesn't take into account added or removed characters).
The correct value should have been 18 (which reads as "The large bird is"), because the master offset ends at "is".
I need an algorithm for slaveOffset() that can handle added and removed characters and find the most likely slave offset. It does not need to be overly accurate but should solve the problem of large deviations caused by character changes.

This is a classic problem in computer science, typically called "data comparison" or simply "diff". The most common algorithms apply Longest Common Subsequence techniques, but in the general case this is a NP-hard problem so various heuristics are applied to get a "good enough" outcome, often tuned by a human in the loop.
Look up some diff algorithms to get some ideas.
In your case you probably want to start with the heuristic of "where does the slave string start to differ from the master and where does it become the same again". The strings match for the first two characters, but the next time you get a sequence of more than 3 characters matching is at the characters , i and s. The points become markers that you can use in your slaveOffset function.

Given a dictionary and a list of letters, make a program learn to generate valid words | Javascript

I'm working on a big machine learning/nlp project and I'm stuck at a small part of it. (PM me, if you want to know what I'm working on exactly.)
I try to code a program in Javascript that learns to generate valid words, only by using all letters of the alphabet.
What I have is a database of 500K different words. It's a big JS object, structured like this (the words are german):
database = {
"um": {id: 1, word: "um", freq: 10938},
"oder": {id: 2, word: "oder", freq: 10257},
"Er": {id: 3, word: "Er", freq: 9323},
...
}
"freq" means frequency obviously. (Maybe this value sometimes gets important but I currently don't use it, so just ignore it.)
The way my program currently works is:
In the first iteration, it generates a completely random word between 2 and 13 letters long and searches for it in the database. If it's there, every letter in the word gets a good rating, if it's not there, they get a bad rating. Also the word length gets rated. If the word is valid, its word length gets a good rating, if it's not, its word length gets a bad rating.
In the iterations after that first one, it doesn't generate a word with random letters and a random word length. It uses probabilities based on the ratings of the letters and the word length.
For example, let's say it found the words "the", "so" and "if" after the first 100 iterations. So the letters "t", "h", "e" and the letters "s", "o", and the letters "i", "f" are good rated, and the word length of 2 and 3 is also good rated. So the word generated in the next iteration will more likely contain these good rated letters than bad rated letters.
Of course, the program also checks if the currently generated word already was generated and if so, then this word doesn't get rated again and it generates a new one.
In theory it should learn the optimal letter frequency and the optimal word-length-frequency by its own and sometimes only generate valid words.
Yeah. Of course this doesn't work. It gets better for the first few iterations, but as soon as it has found all the 2-lettered words it gets worse. I think my whole way how I do this is wrong. I've actually tried it out and have a (not so beautiful) graph after 5000 iterations for you:
Red line: wrong words generated
Green line: right words generated
Yeah. What is the problem here? Am I doing machine learning wrong? And do you have a solution? Some algorithm or trie system?
PS: I'm aware of this, but it's not in JS, I don't understand it and I can't comment on it.

An alternative method would be to use a Markov Model.
Start by counting up the letter frequencies and also word length frequencies in your dictionary. Then, to create a word:
Pick a weighted random number (see below) between 1 and the maximum existing word length. That's how many letters you're going to generate.
For each letter in the word, pick a weighted random letter and add it to the word.
That's an order-0 Markov model. It's based on the frequency of letters that occur in the corpus. It will probably give you results that are similar to the system you have.
You'll get better results from an order-1 Markov model, where instead of computing letter frequencies, you compute bigram (two-letter permutations) frequencies. So to pick the first letter, you choose only from the bigrams that are used to begin words. For subsequent letters, you choose a letter that follows the previously generated letter. That's going to give you somewhat better results than an order-0 model.
An order-2 model is surprisingly effective. See my blog post, Shakespeare vs. Markov, for an example.
A weighted random number is a number selected "at random," but skewed to reflect some distribution. In the English language, for example, the letter 'e' occurs approximately 12.7% of the time. 't' occurs 9.06% of the time, etc. See https://en.wikipedia.org/wiki/Letter_frequency. So you'd want your weighted random number generator's output to approximate that distribution. Or, in your case, you'd want it to approximate the distribution in your corpus. See Weighted random numbers for an example of how that's done.

How do I sort an array of words that represent numbers?

How can we Sort numbers in words (one, two, three) in Javascript (Angularjs)
My array has some numeric words
$scope.Numbers = ["three", "one", "five", "two", ...... "hundred", "four"];
I want the result to be:
one
two
three
four
...
...
...
hundred
I have searched Google for the solution, but I have not found anything
Also i have tried array.sort(), but it is sorting alphabetically.

Here is a simple multi-step solution:
convert the words to numbers.
Sort the array with .sort(function(a,b){ return a-b; }).
convert the array back to words.
We effectively reduced the problem of sorting words to the problem of sorting numbers and the problem of converting numbers to and from words.
The greater picture is that by reusing the solutions of 3 smaller problems we solved a bigger issue. This is a fundamental part of programming anywhere and here in particular - by finding smaller subproblems and applying them to the task at hand we've solved it quickly and without ever having to actually implement a sorting function on words themselves.

Going to elaborate a bit on what people have written in the comments for you. Simply put, the compiler can't know which word is higher or lower than any other, since words are just a collection of chars. It's pretty much like saying: Which word has a higher value, "chicken" or "car"? Or how can the compiler know that you are even writing in English? What happens if you write the numbers in words but in other languages? Basically, to the compiler each string is a set of chars and it doesn't care which letters or words they are since it doesn't matter from its point of view. If you compare it to a number instead, a number is a legit structure which has properties and mathematical rules to follow. I believe this is the reason people are downvoting your question.
There is no basis for a sorting algorithm to start. Thus, you need to convert the strings to integers first, then sort them, and then convert them back to strings if you want to have them ordered - just like Benjamin above explained.

Search string for numbers

I have a javascript chat bot where a person can type into an input box any question they like and hope to get an accurate answer. I can do this but I know I'm going about this all wrong because I don't know what position the number will appear in the sentence. If a person types in exactly:
what's the square root of 5 this works fine.
If he types in things like this it doesn't.
what is the square root of the 5
the square root of 5 is what
do you know what the square root of 5 is
etc
I need to be able to determine where the number appears in the sentence then do the calculation from there. Note the line below is part of a bigger working chatbot. In the line below I'm just trying to be able to answer any square root question regardless of where the number appears in the sentence. I also know there are many pitfalls with an open ended input box where a person can type anything such as spelling errors etc. This is just for entertainment not a serious scientific project. :)
if(
(word[0]=="what's") &&
(word[1]=="the") &&
(word[2]=="square") &&
(word[3]=="root") &&
(word [4]=="of") &&
(input.search(/\d{1,10}/)!=-1) &&
(num_of_words==6)
){
var root= word[5];
if(root<0){
document.result.result.value = "The square root of a negative number is not possible.";
}else{
word[5] = Math.sqrt(root);
word[5] = Math.round(word[5]*100)/100
document.result.result.value = "The square root of "+ root +" is "+ word[5] +".";
}
return true;
}
Just to be clear the bot is written using "If statemments" for a reason. If the input in this case doesn't include the words "what" and "square root" and "some number" the line doesn't trigger and is answered further down by the bot with a generic "I don't know type of response". So I'm hoping any answer will fit the format I am using. Be kind, I'm new here. I like making bots but I'm not much of a programmer. Thanks.

You can do this using a regular expression.
"What is the sqrt of 5?".match(/\d+/g);
["5"]
The output is an array containing all of the numbers found in the string. If you have more than one, like "Is the square root of 100 10?" then it will be
"Is the square root of 100 10?".match(/\d+/g);
["100", "10"]
so you can pick what number you want to use in your script.

You will need to use regular expressions, if you do not know what they are you should look them up as it would take too long to explain them in this response. Here is a useful website for regular expressions in JavaScript https://developer.mozilla.org/en/JavaScript/Guide/Regular_Expressions.
Assuming that you know regular expressions you should first search for numbers and store all the numbers that you find, if no numbers are found print out an error message. As an added note, you may what to consider searching for mathematical constants such as pi or e. This should work
nums = someString./\d+|pi|e/gi
The next part is going to be hard but to boil it down to is core concept, you need to look for key words such as 'square root', 'times', or 'plus'. You should do this word by word going left to right. For example if a user inputs
What is 5 plus 3 minus 8?
you should detect the plus before the minus, while if this is inputted
What is 5 minus 3 plus 8?
You should detect the minus before the plus.
For operations that uses two numbers you need to take the first two numbers that you found and do the operation and replace the two numbers with the result. I am trying to use reverse polish notation if you do not quite understand what I am trying to do, look it up if do not know what it is.
I hope I understood your question correctly and provided some help to coming to a solution because what you asked is very hard but seems like fun. Good luck. Also as a warning I am not considering order of operations in my response.

word decoder by javascript?

Implement the “Word Decoder” game. This game will present the player with a series of scrambled words (up to 20 words) and challenge him/her to attempt to unscramble them. Each time a new word is displayed, and a text input is provided for the user to write the unscrambled word.
Once the player thinks the word has been properly decoded, he clicks on the “Check answer” button. If the player’s answer is correct, his score is increased by one. If his answer is not correct, he is notified and he is then given a different word.
i understood the Question , but i dont know how to generate it , or even how to start it!!
any help please?

To start, try breaking down the problem into things you'll need; think nouns and verbs. This is simply rewriting the problem in new terms. You need:
word: just a string, but it's a noun you'll need, so list it.
dictionary: a collection of words to choose from (during testing, you don't need many)
display: these become HTML elements, since you're working with JS
scrambled word
text input
submit button to check answer
score
"wrong answer" notifier
to scramble a word
to compare words: how can you compare two words to see if one is a permutation of the other? Do it right and anagrams aren't a problem.
to check an answer
to increment score
to notify user of incorrect answer
to present a new scrambled word
Any item beginning with "to" is a verb; anything else is a noun. Nouns become objects, verbs become methods/functions.
The above is mostly a top-down approach, in contrast with bottom-up (note that top-down vs bottom-up isn't an either-or proposition). Other approaches that might help with not knowing where to start are test driven development or its offshoot, behavior driven development. With these you start by defining, in code, what the program should do, then fill in the details to make it do that.
A hint on comparing words: the problem is basically defining an equivalence class—two strings are equivalent if one is a permutation of the other. The permutations of a string, taken together, form the equivalence class for that string; two strings are in the same equivalence class if the strings are equivalent. As the linked document points out, equivalence classes are well represented by picking a single element of the class as the class representative. Lastly, you can turn the equivalence class definition around: two strings are permutations of each other if they are in the same equivalence class.

Look into loading a dictionary via XHR.
there are tons of those available online [http://www.mieliestronk.com/wordlist.html NOTE: it contains some swear words, if you're going to be doing this for academic purposes, since its your homework, you should look for a "clean" list]...
For scrambling the word: make your string into a char array, then find an array shuffle function [they are simple to write, I wrote one for my implementation of Bogosort]...
function shuffle(b)
{
var a = b.concat([]); //makes a copy of B, b won't be changed...
var final = [];
while(a.length != 0)
{
//0 -> a length-1
var targIndex = Math.round((a.length-1)*(Math.random()));
var value = a[targIndex]
a.remove(targIndex);
final.push(value);
}
return final;
}
When the user is done inputting, simply compare input with the answer [case insensitive, ignore spaces] As stated in comments, there are also the possibility of anagrams, so be sure to check for those... perhaps, you could simply verify the word exists in the dictionary.