Editing data-bind cache in Knockout.js

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Preparation code

Preparation code HTML (this will be inserted in the <body> of a valid HTML5 document in standards mode) (useful when testing DOM operations or including libraries)

<div id="main" style="display: none" data-bind="template: 'repeat'">
</div>
<script id="repeat" type="text/html">
  < table > < tr data - bind = "repeat: { foreach: rows, item: '$row' }" > < td data - bind = "repeat: { foreach: $row().cells, item: '$cell', bind: 'text: \'Cell \' + $cell().id()'}" > < /td>
        </tr > < /table>
</script>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js">
</script>
<script src="https://github.com/SteveSanderson/knockout/raw/master/build/output/knockout-latest.debug.js">
</script>
<script type='text/javascript' src="https://raw.github.com/mbest/knockout-repeat/master/knockout-repeat.js">
</script>
<script>
  function Cell(id) {
    this.id = ko.observable(id);
  }

function Row(id) {
    this.id = ko.observable(id);
    this.cells = ko.observableArray();
  }

var viewModel = {
    rows: ko.observableArray()
  };

for (var i = 0; i < 1000; i++) {
    var row = new Row(i);

for (var j = 0; j < 200; j++) {
      row.cells.push(new Cell(i + " - " + j));
    }
    viewModel.rows.push(row);
  }

ko.utils.buildEvalFunction = function(expression, scopeLevels) {
    // Build the source for a function that evaluates "expression"
    // For each scope variable, add an extra level of "with" nesting
    // Example result: with(sc[1]) { with(sc[0]) { return (expression) } }
    var functionBody = "return (" + expression + ")";
    for (var i = 0; i < scopeLevels; i++) {
      functionBody = "with(sc[" + i + "]) { " + functionBody + " } ";
    }
    return new Function("sc", functionBody);
  };

ko.bindingProvider['instance'].bindingCache = {};
  var withoutcache = ko.bindingProvider['instance'].parseBindingsString;
  var withcache = function(bindingsString, bindingContext) {
      try {
        var viewModel = bindingContext['$data'];
        var scopes = (typeof viewModel == 'object' && viewModel != null) ? [viewModel, bindingContext] : [bindingContext];
        var cacheKey = scopes.length + '_' + bindingsString;
        var bindingFunction;
        if (cacheKey in this.bindingCache) {
          bindingFunction = this.bindingCache[cacheKey];
        } else {
          var rewrittenBindings = " { " + ko.jsonExpressionRewriting.insertPropertyAccessorsIntoJson(bindingsString) + " } ";
          bindingFunction = this.bindingCache[cacheKey] = ko.utils.buildEvalFunction(rewrittenBindings, scopes.length);
        }
        return bindingFunction(scopes);
      } catch (ex) {
        throw new Error("Unable to parse bindings.\nMessage: " + ex + ";\nBindings value: " + bindingsString);
      }
      };
</script>

Include JavaScript libraries as follows: <script src="//cdn.ext/library.js"></script>

Define setup for all tests (variables, functions, arrays or other objects that will be used in the tests) (runs before each clocked test loop, outside of the timed code region) (e.g. define local test variables, reset global variables, clear canvas, etc.) (see FAQ)

Define teardown for all tests (runs after each clocked test loop, outside of the timed code region) (see FAQ)

Code snippets to compare

Test 1

Title

Async (check if this is an asynchronous test)

Code

ko.bindingProvider['instance'].parseBindingsString = withcache;

var main = $("#main");
ko.applyBindings(viewModel, main[0]);

Test 2

Title

Async (check if this is an asynchronous test)

Code

ko.bindingProvider['instance'].parseBindingsString = withoutcache;

var main = $("#main");
ko.applyBindings(viewModel, main[0]);