GWT / JS库，用于类似DB的临时存储

Question

I am looking for a library written in either GWT or Javascript that allows me to put data to some kind of structure which would allow me database-like queries.

For example, I might store a number of records and then ask questions like, give me all the records matching certain conditions.

The level of optimization is less important...for example a scan may be appropriate for most applications since this code would be running clientside on small amounts of data.

Answer 1

Library

There's TrimQuery :

For rich web application developers, the TrimQuery engine from TrimPath is a lightweight GPL/APL open-source component that lets you have the power of SQL queries while running in a web browser.

No library

...although for your stated goal, it seems easy enough to loop over array of objects, perhaps using one of the new ES5 Array methods like filter (which are easy enough to add when running in a browser that doesn't have native copies). For instance, if you have an array of objects representing cars, this gives you the blue ones:

// Get only blue cars
var blueCars = store.filter(function(entry) {
    return entry.color === "blue";
});

Live example

Or if you don't want to worry about adding filter to older browsers, just use a simple for loop:

var blueCars, index, entry;

blueCars = [];
for (index = 0; index < store.length; ++index) {
    entry = store[index];
    if (entry && entry.color === "blue") {
        blueCars.push(entry);
    }
}

Here's the store I'm running either of those against:

// The data store
var store = [
    {color: "blue", make: "Toyota"},
    {color: "red", make: "Toyota"},
    {color: "green", make: "Toyota"},
    {color: "blue", make: "Ford"},
    {color: "silver", make: "Ford"},
    {color: "blue", make: "Jaguar"},
    {color: "red", make: "Jaguar"},
    {color: "green", make: "Fiat"}
];

And here's how to add filter if it's not there natively (off-the-cuff implementation, you might look for libraries like es5-shim that try to do a more thorough job, or just use a simple for loop):

// Add `filter` if not already there
if (typeof Array.prototype.filter === "undefined") {
  (function() {
    display("(Added <code>filter</code>, browser didn't have it natively)");
    function Array$filter(callback, thisArg) {
      var index, value, result;

      result = [];
      for (index = 0; index < this.length; ++index) {
        if (this.hasOwnProperty(index)) {
          value = this[index];
          if (callback.call(thisArg, value, index, this)) {
            result.push(value);
          }
        }
      }
      return result;
    }
    if (typeof Object.defineProperty !== "undefined") {
      Object.defineProperty(Array.prototype, "filter", {
        enumerable: false
      });
    }
    else {
      Array.prototype.filter = Array$filter;
    }
  })();
}