JSON serialize to multipart form data

serialize-multipart.js

function serializeMultipart (obj, previous) {
    var pairs = []
    _.each(obj, function (value, key) {
        if (previous !== undefined) {
            key = previous + '[' + key + ']'
        }

        if (_.isArray(value)) {
            _.each(value, function (value) {
                pairs.push([key + '[]', value])
            })
            return
        }

        if (_.isObject(value)) {
            var children = serializeMultipart(value, key)
            Array.prototype.push.apply(pairs, children)
            return
        }

        if (value != null) {
            pairs.push([key, value.toString()])
        }
    })
    return pairs
}