I am trying to call startsWith() string function on a JSON property value:
{"message":"xyzabc"}
var jsonResponse = JSON.parse(httpResponse.text);
var stringMessage = jsonResponse.message.toString();
if(stringMessage.startsWith('xyz')) {
...
}
but I get the error:
Object xyzabc has no method 'startsWith'
How can I do that?
The code is running on server side, Express on Node.js
It may be happen that your browser does not support the startsWith() function so you can use use the RegExp to overcame this problem like this...
var jsonObject={message:"xyzHELLO"};
var regex=new RegExp("^xyz");
if(regex.test(jsonObject["message"])){
alert("hello");
}
[EDIT]
If you want to add the function startsWith() in your each and every string than you can add like this
if (String.prototype.startsWith !== "function") {
String.prototype.startsWith = function (searching) {
var regex = new RegExp("^" + searching);
if (regex.test(this.toString())) {
return true;
}
else {
return false;
}
}
}
and after that you can use like this:
var jsonObject = { message: "xyzHELLO" };
if (jsonObject["message"].toString().startsWith("xyz")) {
alert("start with");
}
else {
alert("not start with");
}
[EDIT]
if (String.prototype.startsWith !== "function") {
String.prototype.startsWith = function (searching) {
if (this.toString().indexOf(searching) == 0) {
return true;
}
else {
return false;
}
}
}
As per the comment by @nnnnnn and I also think it is good practice if we use the native function of the JavaScript, Thanks @nnnnnn.
question at that time you does not describe it.yourString.startsWith() function than you can also add that function in the in the String class
Please double check your input JSON. Your code works like a charm with a correct JSON input in httpResponse.text.
var json = '{"message": "xyztest"}';
var jsonResponse = JSON.parse(json);
var stringMessage = jsonResponse.message.toString();
if(stringMessage.startsWith('xyz')) {
alert('It works!');
}
Also please make sure the browser you are working in supports startsWith method. Here you can find a list with all supported browsers.
If you need to work around the browser compatibility issues, you can use the widely supported indexOf method.
if(stringMessage.indexOf('xyz') === 0) {
alert('It works!');
}
HERE is a Fiddle for both cases.
Apparently, Js has startsWith function for the strings. However, using your own function to see if the string starts with the value should cause no error.
function StartsWith(s1, s2) {
return (s1.length >= s2.length && s1.substr(0, s2.length) == s2);
}
var jsonResponse = JSON.parse(httpResponse.text);
var stringMessage = jsonResponse.message.toString();
if(StartsWith(stringMessage,'xyz')) {
//Doing Stuff!
}
.messagein yourjsonResponse? It's hard to think out why something does not work, when you don't even know how does it look like!.startsWith()? Also, you're not operating on a JSON property value, you've called.toString()on an object property value, and are using.startsWith()on the result. There's no such thing as a JSON object.