FAQ

FAQ

How can I do asynchronous validation?

You can't. lewd is meant to do syntactic validation of your data, which can practically always be done synchronously. Support of asynchronous conditions is something I would like to add at some point, but there are no concrete plans as of now.

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lewd errors don't say where a problem occurred!

The exception that is thrown contains that information, but it is not shown when it is output to the console via console.log and the like. Instead, force a serialization so that the exception's toString method is called:

lewd({ x: Number })({ x: 'not a number' });
// outputs "ConditionViolationException: must be of type number"

try {
    lewd({ x: Number })({ x: 'not a number' });
} catch (e) {
    console.log(e.toString());
    // outputs "Condition violation at "/x": must be of type number"
}

For more details see the handling validation failures section.

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Why do my default values behave strangely?

Be careful when using non-primitive values for defaults. Since they are passed by reference you might get unexpected (and unwanted) side effects:

var condition = lewd({
    x: lewd(Array).optional().default([])
});

var value_one = c({});
value_one.x.push(42);
// value_one is { x: [42] }

var value_two = c({});
// value_two also is { x: [42] } !

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Can I use lewd in a browser environment?

As of 0.6.0, experimental browser support is available in the dist folder as a UMD module. Beware, though, that the browser builds are not yet run against our test suite, only the Node.JS source is (hence the "experimental").

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Are recursive definitions supported?

No, and they probably never will be. If you have documents of that complexity you should probably take a look at json-schema.

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lewd() with an object and options doesn't work!

If you are trying to do something like this:

lewd({ x: Number, y: String }, { byDefault: 'optional' });

lewd will not interpret the second argument as options to the first but as two independent conditions (which is why you can write lewd(String, Number) to match either a string or a number). What you will have to do is use the object condition explicitly:

lewd.object({ x: Number, y: String }, { byDefault: 'optional' });

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Why not simply use validator.js?

validator.js is a great library but it scratches a different itch. It only works with strings, which is great for URLs and query parameters but doesn't really help you validating the JSON payload of your run-of-the-mill AJAX request. However, lewd comes with condition wrappers for many of validator's validation functions so you get the best of both worlds.