kvetch.js

/* - Public Domain software by Colten Jackson
 * - make a global method to prefer over 'fetch' api 
 * - pass an object to convert key:value pairs to a properly encoded querystring (k:v, hence, kvetch)
 * - use a Proxy with a getter so you can call 'kvetch.get()','kvetch.put()','kvetch.delete()' and so on with a single function
 * * */
(function(){
    let kv2query = kv => Object.keys(kv || {}).map(key => {
            var value = kv[key]
            return encodeURIComponent(key) + '=' + encodeURIComponent(value)
        }).join('&')

    let bodyBuilder = body => {
        let bodyType = body && body.constructor
        /* if bodyType if falsey, assign an empty object, no change */
        if(!bodyType) return {}
        /* if bodyType is formdata, hand the body back and let fetch assign content header automatically */
        else if(bodyType == FormData) return {body}
        /* otherwise, stringify objects and set content type to go with it */
        else return {
            body: bodyType == Object ? JSON.stringify(body) : body,
            headers: {
                'Content-Type': bodyType == ArrayBuffer ? 'application/octet-stream' :
                                bodyType == Object ? 'application/json' : 'text/plain'
            }
        }
    }

    window.kvetch = new Proxy({}, {
        get: (target, name) => {
            return (url, queryObject = {}, optionalBody) => {
                /* can't do anything with an url */
                if(!url || url.constructor != String) throw new Error("first argument URL must be a string.")
                /* it's okay if queryObject is left blank, but if its truthy it better be an object */
                if(queryObject && queryObject.constructor != Object) throw new Error("second argument QueryObject must be an object or nothing at all.")
                /* optionalBody will have to switch between content types for string, object -> JSON, or raw byte array */

                options = Object.assign({
                    method: name.toUpperCase(),
                    credentials: 'same-origin',
                    redirect: 'error'
                }, bodyBuilder(optionalBody))

                return fetch(url + '?' + kv2query(queryObject), options).then(response => {
                    // actually I'd prefer it if error codes got thrown to a catch block
                    if(!response.ok) throw new Error(response); 
                    else return response; 
                })
            }
        }
    })
})()