AJAX: Check if a string is JSON?

Question

My JavaScript sometimes crashes on this line:

var json = eval(\'(\' + this.responseText + \')\');

Crashes are caused when the argument of <

Answer 1

Why you can't just check what is the response? It is more more efficient.

var result;

if (response.headers['Content-Type'] === 'application/json')
    result = JSON.parse(this.responseText);
else
    result = this.responseText;

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