SharePoint read Host web query string in App Part

Read Host web values in App web 
Problem Statement: I have to read Host web Query string value in App web.
Steps:
 Read query string from url.
 Create a property bag in host web, push query string in to property bag In app web read Property bag  values and use it.
Solution:
Add Script Editor webpart then add below code
 Read query string and create property bag

	<script type="text/javascript">
	$(document).ready(function () {
	var queryStringValue = GetUrlKeyValue('MyPropertyName', window.location.href);
	if(!queryStringValue){
	queryStringValue="0";
	}
	SP.SOD.executeFunc('sp.js', 'SP.ClientContext', writeProperty("MyPropertyName",queryStringValue));
	});
	function writeProperty(propertyName, propertyValue) {
	var clientContext;
	clientContext = SP.ClientContext.get_current();
	var web = clientContext.get_site().get_rootWeb();
	this.props = web.get_allProperties();
	this.props.set_item(propertyName, propertyValue);
	web.update();
	clientContext.executeQueryAsync(Function.createDelegate(this, writePropertySuccess), Function.createDelegate(this, writePropertyFailed));
	}
	function writePropertySuccess(){
	var nid = SP.UI.Notify.addNotification("Property registered", false);
	}
	function writePropertyFailed(sender, args){
	var nid = SP.UI.Notify.addNotification("Failure while trying to write the property: " + args.get_message(), false);
	}
	</script>

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In App part, write below code, where you want to use query string value.
Read property bag in SharePoint App

	<script type="text/javascript" src="/_layouts/15/MicrosoftAjax.js"></script>
	<script type="text/javascript" src="/_layouts/15/sp.runtime.js"></script>
	<script type="text/javascript" src="/_layouts/15/sp.js"></script>
	<script type="text/javascript">
	$(document).ready(function () {
	var hostweburl = decodeURIComponent(getQueryStringParameter("SPHostUrl"));
	var scriptbase = hostweburl + '/_layouts/15/';
	$.getScript(scriptbase + 'SP.Runtime.js',
	function () {
	$.getScript(scriptbase + 'SP.js',
	function () { $.getScript(scriptbase + 'SP.RequestExecutor.js', readProperty(hostweburl)); }
	);
	}
	);
	});
	function readProperty(hostweburl) {
	var appweburl = decodeURIComponent(getQueryStringParameter("SPAppWebUrl"));
	var clientContext = new SP.ClientContext.get_current();
	var hostContext = new SP.AppContextSite(clientContext, hostweburl);
	var web = hostContext.get_web();
	clientContext.load(web);
	webProperties = web.get_allProperties();
	clientContext.load(webProperties);
	clientContext.executeQueryAsync(propertiesSucceeded, propertiesFailed);
	}
	function propertiesSucceeded() {
	var allProps = webProperties.get_fieldValues();
	var customProp = "";
	//Check for My property.
	//My Property name is: MyPropertyName
	if (webProperties.get_fieldValues().MyPropertyName != undefined) {
	var customProp = webProperties.get_fieldValues().MyPropertyName;
	alert("Value from App" + customProp);
	}
	}
	function propertiesFailed(args, sender) {
	alert("failed");
	}
	function getQueryStringParameter(param) {
	var params = document.URL.split("?")[1].split("&");
	var strParams = "";
	for (var i = 0; i < params.length; i = i + 1) {
	var singleParam = params[i].split("=");
	if (singleParam[0] == param) {
	return singleParam[1];
	}
	}
	}
	</script>

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