如何在javascript中操纵字符串？

Question

I'm new to javascript and need some help! I want to make a magic 8-ball script that pulls a specific answer for certain questions. So far I have it so that if I ask a specific question, it will give me one answer, but I want to alter it so that it will give me a specific answer based on whether or not the question uses 'who' or 'what' or if a question uses an 'a' 'd' and 'b' and things like that. Does anyone know how to do this and could you possibly help me? I'm completely stuck and don't know how to go about this. Thank you for your help!

    <script>


        function eightBall() {
            var answer = document.getElementById("answerBox").value;
            var images = ['answerYes.png', 'answerNo.png', 'answerAskLater.png', 'answerNotL.png', 'answerMaybe.png'];

            if (answer.search(/Will I be rich?/) > -1) {
                var askLater = '../images/answerAskLater.png'
                document.getElementById('eightTemplate').src = askLater;

            } else if (answer.search(/Will I be happy?/) > -1) {
                var no = '../images/answerNo.png'
                document.getElementById('eightTemplate').src = no;
            } else if (answer.search(/Will I live to be 90 years old?/) > -1) {
                var yes = '../images/answerYes.png'
                document.getElementById('eightTemplate').src = yes;
            } else if (answer.search(/Will I be married later in life?/) > -1) {
                var notLikely = '../images/answerNotL.png'
                document.getElementById('eightTemplate').src = notLikely;
            } else if (answer.search(/Can I have a puppy?/) > -1) {
                var maybe = '../images/answerMaybe.png'
                document.getElementById('eightTemplate').src = maybe;
            }

        }


    </script>

Answer 1

If you want to see if a question contains a certain word, then I would suggest using javascript's Regular Expressions . these expressions can be used to test or extract certain words or even sentence structures. For instance:

var questionPattern = new RegExp('.+\?$');

//returns true if answer ends with question mark
var isQuestion = questionPattern.test(answer); 

You're actually already using regular expressions without even knowing it. Everything you passed to the search function is a regular expression in short hand. Example:

/.+\?$/

is the shorthand way of declared the same regular expression i did in the above code. You can also construct regular expressions to see if a string begins with the word what:

/^(what)/i

For more information on regular expressions, check here . Hope it helps!

Answer 2

Instead of lots of similar if/then/else statements, I suggest putting all the cases in a table, so you can loop over it.

function eightBall() {
    var possibilities = [
        { match: /Will I be rich\?/,
          answer: 'AskLater' },
        { match: /Will I be happy\?/,
          answer: 'No' },
        ...
    ];
    var answer = document.getElementById('answerBox').value;
    for (var i = 0; i < possibilities.length; i++) {
        if (possibilities[i].test(answer)) {
            document.getElementById('eightTemplate').src = '../images/answer' + possibilities[i].answer + '.png';
            return;
        }
    }
    // Display a default answer here
}

You can add regular expressions matching who , what , letters, or anything else to the possibilities table.

Answer 3

There is also a simpler way to achieve this: str.toLowerCase().contains("who"); but RegExp is your choice for complicated checks.

Answer 4

The thing between the slashes doesn't have to match the entire string. The following will show answerYes.png if the string contains a lowercase 'b' anywhere. For example, it will match when the string is "Do you like blueberries?" or "abcd".

else if (answer.search(/b/) > -1) {
    var yes = '../images/answerYes.png'
    document.getElementById('eightTemplate').src = yes;
}

For clarity, it's probably a good idea to rename your answer variable to question , since it looks like you're using it to hold the value of the question.

This approach will probably be fine for what you're doing. It will work as long as all you want to do is simply find a word, letter, or phrase in the question. If you want to get more sophisticated, and match a general pattern instead of a specific string of text, you may want to learn about regular expressions (RegExp) as others have suggested.