Adds a textarea to the top of the page that can execute javascript within the page. Useful for testing code on mobile browsers.

bookmarklet.js

javascript:var%20codeEval%3Ddocument.createElement(%22div%22)%2CinputBox%3Ddocument.createElement(%22textarea%22%2C%7Brows%3A200%2Ccols%3A800%7D)%2CevalButton%3Ddocument.createElement(%22button%22)%2CbuttonText%3Ddocument.createTextNode(%22Eval%22)%3BevalButton.appendChild(buttonText)%2CcodeEval.appendChild(inputBox)%2CcodeEval.appendChild(evalButton)%2Cdocument.body.insertBefore(codeEval%2Cdocument.body.firstElementChild)%2CevalButton.addEventListener(%22click%22%2Cfunction()%7Beval(inputBox.value)%7D)%3B

CodeEvalBox.js

var codeEval = document.createElement('div');
var inputBox = document.createElement('textarea', { rows: 200, cols: 800 });
var evalButton = document.createElement('button');
var buttonText = document.createTextNode('Eval');
evalButton.appendChild(buttonText);
codeEval.appendChild(inputBox);
codeEval.appendChild(evalButton);
document.body.insertBefore(codeEval, document.body.firstElementChild);
evalButton.addEventListener('click', function () { eval(inputBox.value)});

CodeEvalBox.min.js

var codeEval=document.createElement("div"),inputBox=document.createElement("textarea",{rows:200,cols:800}),evalButton=document.createElement("button"),buttonText=document.createTextNode("Eval");evalButton.appendChild(buttonText),codeEval.appendChild(inputBox),codeEval.appendChild(evalButton),document.body.insertBefore(codeEval,document.body.firstElementChild),evalButton.addEventListener("click",function(){eval(inputBox.value)});