It's not as simple as it could be, that's why you are having problems finding good examples. Here's an annotated example that does just what you're asking for: on('ready',function() {
'use strict';
// Threshold to be equal to or less than to get removed
var threshold = 0;
// Activate on a change to the value of bar1
on('change:graphic:bar1_value',function(obj){
var turnorder;
// if the value is below or equal
if( obj.get('bar1_value') <= threshold ){
// grab the current turnorder
turnorder = Campaign().get('turnorder');
// if it's the empty string, then just treat it as an array,
// otherwise decode it as a JSON string into the array of turns
turnorder = ('' === turnorder) ? [] : JSON.parse(turnorder);
// Get a version of it without the token we were activated for
turnorder = _.reject(turnorder, function(i){
return obj.id === i.id;
});
// encode the array as a JSON string and
// stuff it back in the turnorder property of the Campaign
Campaign().set('turnorder',JSON.stringify(turnorder));
}
});
});
Feel free to ask me anything, I'm happy to discuss the API at length! =D