Determining if two words share a letter

jolwalton

Any hints about how I'd tackle this in Twine Harlowe?

E.g. I'd want a positive result if the words were "eyes" and "smile" (both contain e and s), or a negative result if the words were "eyes" and "blink" (no letters in common).

Something to do with splitting a string into an array of substrings for starters, I guess

Thank you!

greyelf

note: A more experienced Javascript coder may be able to supply a better solutions.

You could use a combination of Javascript's String split() method, the new Array some() method and an inline function to do what you want. It would look something like the following.

"eyes".split('').some(function(c){return "smile".indexOf(c) !== -1;})

or (a slightly more readable version)

"eyes".split('').some(
	function(c) {
		return "smile".indexOf(c) !== -1;
	}
);

But there are two issues with the above:

1. The Array some() method may not exist in older web-browsers, which you can solve by adding the following Polyfill from MDN to the start of your Story Javascript area.

// Polyfill for Array some() method.
// Production steps of ECMA-262, Edition 5, 15.4.4.17
// Reference: http://es5.github.io/#x15.4.4.17
if (!Array.prototype.some) {
  Array.prototype.some = function(fun/*, thisArg*/) {
    'use strict';

    if (this == null) {
      throw new TypeError('Array.prototype.some called on null or undefined');
    }

    if (typeof fun !== 'function') {
      throw new TypeError();
    }

    var t = Object(this);
    var len = t.length >>> 0;

    var thisArg = arguments.length >= 2 ? arguments[1] : void 0;
    for (var i = 0; i < len; i++) {
      if (i in t && fun.call(thisArg, t[i], i, t)) {
        return true;
      }
    }

    return false;
  };
}

2. Harlowe has problems parsing the expression and throws a "Unexpected token" error for the following.

result: (print: "eyes".split('').some(function(c){return "smile".indexOf(c) !== -1;}))

You can get around this issue by creating a custom method and using that instead. There are two ways you can do this:

a. Create a Custom Namespace to contain your new method.

Add the following to your Story Javascript area, it creates a new My namespace and assigns a new containsCharacters method to that namespace. This code needs to appear later in the passage than the Array some() method Polyfill.

if (typeof window.My == "undefined") {
  window.My = {};
}
Object.defineProperty(window.My, 'containsCharacters', {
	value(str, searchValue) {
		// Check if a valid str value was supplied.
		if (typeof str !== 'string' || typeof searchValue !== 'string') {
			return false;
		}

		return searchValue.split('').some(function(c){return str.indexOf(c) !== -1;})
	}
});

... to use the new method add the following to a passage, it creates three variables and then checks if the characters in two of them are contained within the third.

(set: $wordA to "eyes")
(set: $wordB to "smile")
(set: $wordC to "blink")

check 1: (print: My.containsCharacters($wordA, $wordB))
check 2: (print: My.containsCharacters($wordA, $wordC))

b. Extend the built-in Javascript String prototype.

warning: This technique is consider bad by some (many?) because it can interfere with current (or future) Standard methods added by web-browser developers.

Add the following to your Story Javascript area, it extends the built-in Sting prototype to include a new containsCharacters method. This code needs to appear later in the passage than the Array some() method Polyfill.

Object.defineProperty(String.prototype, 'containsCharacters', {
	value(searchValue) {
		// Lazy equality for null.
		if (this == null) {
			throw new TypeError('String.prototype.containsCharacters called on null or undefined');
		}

		// Check if a valid searchValue was supplied.
		if (typeof searchValue !== 'string') {
			return false;
		}

		var str = this;
		return searchValue.split('').some(function(c){return str.indexOf(c) !== -1;})
	}
});

... to use the new method add the following to a passage, it creates three variables and then checks if the characters in two of them are contained within the third.

(set: $wordA to "eyes")
(set: $wordB to "smile")
(set: $wordC to "blink")

check 1: (print: $wordA.containsCharacters($wordB))
check 2: (print: $wordA.containsCharacters($wordC))

jolwalton

Oh my God, brilliant. Thanks so much. This will level me up once I get my head around it.