Given a string describing a Javascript function, convert it to a Javascript function

Question

Say I\'ve got a Javascript string like the following

var fnStr = \"function(){blah1;blah2;blah3; }\" ;

(This may be from an expression the

Answer 1

You can do this:

//in your case: eval("var fn = " + fnStr);
eval("var fn = function(){ blah1;blah2;blah3; }"); 
fn();

Not sure how to get it much simpler, sometimes there's no (better) way around eval(). Here's a quick example of this in action.

Answer 2

You can call Parse your string as javascript fuction

1. function getDate(){alert('done')} // suppose this is your defined function

to call above function getDate() is this in string format like 'getDate()'

2. var callFunc=new Function('getDate()') //Parse and register your function

3. callFunc() // Call the function

Answer 3

Use parentheses.

var fn = eval("(function() {...})");

This technique is also good for transmitting JSON values.

By the way, it's often better to build functions by composing them directly from other functions. If you are using strings, you have to worry about things like unexpected variable capture.

Answer 4

Here's what I use for simple cases:

// an example function
function plus(...args) {
    return args.reduce( (s,v) => s+v, 0 );
}

// function to string
let str = plus.toString();

// string to function
let copy = new Function('return ' + str)();

// tests
console.assert(plus.name == 'plus');
console.assert(copy.name == 'plus');
console.assert(plus.constructor == Function);
console.assert(copy.constructor == Function);
console.assert(plus(1,2,3,4) === copy(1,2,3,4));
console.assert(plus.toString() === copy.toString());

Answer 5

There's also the Function object.

var adder = new Function("a", "b", "return a + b");

Answer 6

You can also insert the string into a script element and then insert the script element into the page.

script_ele = window.document.createElement("script");
script_ele.innerHTML = 'function my_function(){alert("hi!");}';
window.document.body.appendChild(script_ele);
my_function();