How to decode JSON-like JavaScript Object Literal Strings

Question

I'm having trouble decoding an array of strings from what I thought was JSON.

var result = [
  "{gene: 'PEX2', go_bp: '0.766500871709', CombinedPvalue: '9.999999995E-4'}",
  "{gene: 'PEX5', go_bp: '0.766472586087', CombinedPvalue: '9.999999995E-4'}",
  "{gene: 'PEX7', go_bp: '0.766386859737', CombinedPvalue: '9.999999995E-4'}"
];

You can see that there are 3 gene-related strings of JavaScript object literals, each encoded as a string. How can I decode these?

I tried JSON.parse but it gives me an error.

for (var i = 0; i < result.length; i++) 
    console.log(JSON.parse(result[i]));

Uncaught SyntaxError: Unexpected token g.

Is there a simple way?

What you have is not JSON. Seems like strings containing JS object literals. The best solution would be to fix the code that generates these strings. — Felix Kling
– Felix Kling, Commented Jun 16, 2015 at 2:10
It is an array of almost-JSON. See json.org for proper format. — Paul
– Paul, Commented Jun 16, 2015 at 2:11
JSON string should be in this format: {"key": "value"} not {key : "value"}. — TaoPR
– TaoPR, Commented Jun 16, 2015 at 2:12
It's also likely that you don't want to quote the numeric values. — dschultz
– dschultz, Commented Jun 16, 2015 at 2:24

Daniel Gimenez · Accepted Answer · 2015-06-16 02:37:48Z

5

Since this is valid javascript, you can use Function() to return a new instance of the object by creating an anonymous function and then immediately executing it. Unlike the other answer with eval(), you don't have to declare a variable and assign the object literal to that variable in the string passed to eval - everything you need can be done cleanly in one line.

var result = [
    "{gene: 'PEX2', go_bp: '0.766500871709', CombinedPvalue: '9.999999995E-4'}",
    "{gene: 'PEX5', go_bp: '0.766472586087', CombinedPvalue: '9.999999995E-4'}",
    "{gene: 'PEX7', go_bp: '0.766386859737', CombinedPvalue: '9.999999995E-4'}"
];

for (var i = 0; i < result.length; i++) {
    // create function that returns the obj literal
    // and call it immedieately.
    var obj = new Function( 'return ' + result[i] + ';' )();
    document.write('gene: ' + obj.gene + ' <br />');
}

edited Jun 16, 2015 at 2:37

answered Jun 16, 2015 at 2:18

Daniel Gimenez

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2 Comments

Eric McCormick Over a year ago

Excellent use of Function to avoid an eval.

Chris Tavares Over a year ago

It's not really avoiding an eval, it's just using another way to do it.

user1864610 · Accepted Answer · 2015-06-16 02:16:58Z

3

What you have is not JSON, but Javascript objects in text form. You can convert them to Javascript objects with eval():

    var result = [
      "{gene: 'PEX2', go_bp: '0.766500871709', CombinedPvalue: '9.999999995E-4'}",
      "{gene: 'PEX5', go_bp: '0.766472586087', CombinedPvalue: '9.999999995E-4'}",
      "{gene: 'PEX7', go_bp: '0.766386859737', CombinedPvalue: '9.999999995E-4'}"
    ];

    var f;
    for (var i = 0; i < result.length; i++) {
        eval("f = "+result[i]);
        console.log(f.gene);
    }

Note: eval is generally held to be evil. In this case it's safe enough if you're absolutely sure that the source array will only ever hold data, and no code.

answered Jun 16, 2015 at 2:16

user1864610

Comments

JAAulde · Accepted Answer · 2015-06-16 02:19:56Z

1

The JSON format requires double quotes around property names. Your sample data lacks these quotes, and this is not valid JSON.

It also requires double quoted values, not single quoted.

Try something like this:

   '{"gene": "PEX2", "go_bp": "0.766500871709", "CombinedPvalue": "9.999999995E-4"}',

edited Jun 16, 2015 at 2:19

JAAulde

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answered Jun 16, 2015 at 2:16

Chris Tavares

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