How to dynamically inject a JavaScript function?

问题

I am stuck using a product with a horrible UI at work and trying to make it palatable via UserScripts in Chrome. To that end, I am trying to inject a JavaScript function into the page via the UserScripts mechanism:

// find the div
var dropDown = document.getElementById("tstGlobalNavigation_ddlChooseProject");

// inject function
dropDown.innerHTML = dropDown.innerHTML + "<script>function gotoIncident(){alert('111')}</script>";        

// inject a button
dropDown.innerHTML = dropDown.innerHTML + "&nbsp;&nbsp;&nbsp;<input type='button' name='btnSearch' value='Go' onClick='javascript:gotoIncident()' >";

As you can see I am injecting a button and a function (gotoIncident) that should fire when the user clicks the button.

The button does appear on the screen but when I click it, the javascript debugger tells me that gotoIncident is not defined.

What am I missing?

回答1:

Inject a <script> tag into the <head> which contains a self-invoking function:

var head = document.getElementsByTagName('head')[0],
    script = document.createElement('script');

script.src = 'path/to/script.js';    
head.appendChild(script);

Where the referenced script looks something like this:

(function(){
    // do your stuff here    
})();

Edit

How to do it as an inline script:

function fn() {
    alert('hello JS');
}

var head = ...,
    script = ...;

// FF doesn't support innerText
script[script.innerText ? 'innerText' : 'textContent'] = '(' + fn + ')()';
head.appendChild(script);

Demo

回答2:

You need to define the function in the global scope (put it in the <head> section) to use it where you do.

回答3:

For reference I resolved it the following way:

myDiv.innerHTML = myDiv.innerHTML + " <input type='text' id='txtSearch' name='txtSearch' style='position:absolute;top:8px;left:800px;width:50px' >";
myDiv.innerHTML = myDiv.innerHTML + " <input type='button' name='btnSearch' value='Go' onclick='fn()' style='position:absolute;top:8px;left:860px;width:35px'>";

addScript("function fn() {var obj = document.getElementById('txtSearch'); "
  + "if (obj != null) { "
  + "  var incidentId = document.getElementById('txtSearch').value; "
  + "  var currentURL = location.href; "
  + "  var splitResult = currentURL.split('/'); "
  + "  var projectId = splitResult[4]; "
  + "  location.href = 'http://site/SpiraTeam/' + projectId + '/Incident/' + incidentId + '.aspx'; "
  + " } }"
  , "fn");

}

来源：https://stackoverflow.com/questions/5574231/how-to-dynamically-inject-a-javascript-function

标签

javascript

google-chrome

javascript-events

userscripts