Using a variable key in chrome.storage.local.set [duplicate]

Answer 1

I have solved the problem. Instead of using chrome.storage.local.set({key:val[key]+param1});

I have replaced the json string {key:val[key]+param1} with an object.

var obj = {};       
var key = "myKey";  
obj[key] += param1;   
chrome.storage.local.set(obj);

Here obj has value {"myKey":"the appended value"}

Answer 2

In JavaScript, the only way to use a non-static variable name is by assigning a value as a property, instead of using object literals.

var key = 'myKey';
var param1 = 'whatever';
chrome.storage.local.get(key, function(val) {
    // Create property if does not exist (yet)
    if (typeof val[key] != 'string') val[key] = '';
    // Append value of param1
    val[key] += param1;
    // Save data
    chrome.storage.local.set(val);
    alert(val[key]);
});

Note: You might want to verify that set succeeded. This can be done by using a callback. For instance:

    chrome.storage.local.set(val, function() {
        if (chrome.extension.lastError) {
            alert('An error occurred: ' + chrome.extension.lastError.message);
        }
    });