toQueryString.js

toQueryString.js

function toQueryString(obj, urlEncode) {
	//
	// Helper function that flattens an object, retaining key structer as a path array:
	//
	// Input: { prop1: 'x', prop2: { y: 1, z: 2 } }
	// Example output: [
	//     { path: [ 'prop1' ],      val: 'x' },
	//     { path: [ 'prop2', 'y' ], val: '1' },
	//     { path: [ 'prop2', 'z' ], val: '2' }
	// ]
	//
	function flattenObj(x, path) {
		let result = [ ]

		path = path || []
		Object.keys(x).forEach(key => {
			if (!x.hasOwnProperty(key))
				return

			let newPath = path.slice()
			newPath.push(key)

			let vals = [ ]
			if (typeof x[key] == 'object') {
				 vals = flattenObj(x[key], newPath)
			} else {
				vals.push({ path: newPath, val: x[key] })
			}
			vals.forEach(obj => result.push(obj))
		})

		return result
	} // flattenObj

	// start with  flattening `obj`
	let parts = flattenObj(obj) // [ { path: [ ...parts ], val: ... }, ... ]

	// convert to array notation:
	parts = parts.map(varInfo => {
		if (varInfo.path.length == 1)
			varInfo.path = varInfo.path[0]
		else {
			let first = varInfo.path[0]
			let rest = varInfo.path.slice(1)
			varInfo.path = first + '[' + rest.join('][') + ']'
		}
		return varInfo
	}) // parts.map

	// join the parts to a query-string url-component
	let queryString = parts.map(varInfo => varInfo.path + '=' + varInfo.val).join('&')
	if (urlEncode)
		return encodeURIComponent(queryString)
	else
		return queryString
}