javascriptarraysassociative

JavaScript "associative" array access

I have a simple simulated array with two elements:

bowl["fruit"] = "apple";
bowl["nuts"] = "brazilian";

I can access the value with an event like this:

onclick = "testButton00_('fruit')">with `testButton00_`

function testButton00_(key){
    var t = bowl[key];
    alert("testButton00_: value = "+t);
}

However, whenever I try to access the array from within code with a key that is just a non-explicit string, I get undefined. Do I have somehow have to pass the parameter with the escaped 'key'?

Solution

  • The key can be a dynamically computed string. Give an example of something you pass that doesn't work.

    Given:

    var bowl = {}; // empty object

    You can say:

    bowl["fruit"] = "apple";

    Or:

    bowl.fruit = "apple"; // NB. `fruit` is not a string variable here

    Or even:

    var fruit = "fruit";
bowl[fruit] = "apple"; // now it is a string variable! Note the [ ]

    Or if you really want to:

    bowl["f" + "r" + "u" + "i" + "t"] = "apple";

    Those all have the same effect on the bowl object. And then you can use the corresponding patterns to retrieve values:

    var value = bowl["fruit"];
var value = bowl.fruit; // fruit is a hard-coded property name
var value = bowl[fruit]; // fruit must be a variable containing the string "fruit"
var value = bowl["f" + "r" + "u" + "i" + "t"];