I have a json string like this:
json = "{'run': 'function() { console.log('running...'); }'}"
How do I run that function inside of the json string?
6 Answers
You're going to have to use the eval() (doc) function. A lot of people have a lot of feelings about this function. JSON is best for transporting data, not functions (see JSON). The functions ought to lay in the script on the page.
Also there's a syntax error in your posted code (function is wrapped in single quotes ('), and so is console.log's first parameter).
But...
json = "{\"run\":\"function() { console.log('running...'); }\"}"; //Fixed, thanks
obj = JSON.parse(json);
eval(obj.run); //Logs "running..."
Update:
Oh, and I was mistaken. Eval doesn't seem to like anonymous functions. With the revised code, it will parse json into an object with a run property that is a String, with value "function() { console.log('running...'); }". But when you eval(obj.run);, you will get a SyntaxError declaring an unexpected (. Presumably, this is the ( in function ().
So, I can think of two ways of dealing with this:
- Remove the anonymous function in your actual JSON string (so, make your PHP forget about
function () {), and eval it. This means it will be called as soon as youevalit. What I think you want, is to be able to evaluate it to an anonymous function, that will be called when you want. So, you could write a wrapper function (you would need to follow option 1 for this as well):
function returnEval(str) { return function () { eval(str); } }This would allow you to call it. So:
obj = JSON.parse(json); obj.run = returnEval(obj.run); obj.run(); //Logs "running..."
Hope this helps!
JSON is not really intended for that, but here seems to be a good example.
1 Comment
ajsie
CouchDB is using this to store map reduce functions in the database. I have to store functions in the database too.
This works for me in Firefox:
var json = "{'run': 'function() { console.log(\\'running...\\'); }'}";
eval('var j = ' + json);
eval('var r = ' + j.run);
r();
Comments
Try this, it works:
var JS = { "function" : "alert( new Date().getTime() );" };
new Function ( "", JS["function"] )();
for nested functions you also can use something like this:
jQuery.each( JS, function( method, value ) {
new Function ( "a, b", "if ( a == 'function' ) { new Function ( '', b )(); }" )( method, value );
} );
Comments
I know that thread is old but i want to share with you guys. You can make string a json and parse it easily with these functions.
function makeString(val){
return JSON.stringify(val, function (key, value) {if (typeof value == 'function') {return value.toString();}return value;});
}
function parseIt(val){
return JSON.parse(string, function (key, value) {if (value.toString().search("function")>-1) {eval("var func = " + value);return func;}return value;});
}
Comments
Without using eval('function()') you could to create a new function using new Function(strName). The below code was tested using FF, Chrome, IE.
<html>
<body>
<button onclick="test()">Try it</button>
</body>
</html>
<script type="text/javascript">
function test() {
try {
var myJSONObject = {"success" : true, "jsFunc" : "myFunction()"};
var fnName = myJSONObject.jsFunc;
var fn = new Function(fnName);
fn();
} catch (err) {
console.log("error:"+err.message);
}
}
function myFunction() {
console.log('Executing myFunction()');
}
</script>
eval(json.substring(10, json.length-2))();? =)