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<head>
<meta charset="utf-8">
<title>Blockly Demo: Step Execution with JS Interpreter</title>
<script src="acorn_interpreter.js"></script>
<script src="../../blockly_compressed.js"></script>
<script src="../../blocks_compressed.js"></script>
<script src="../../javascript_compressed.js"></script>
<script src="../../msg/js/en.js"></script>
<style>
body {
background-color: #fff;
font-family: sans-serif;
}
h1 {
font-weight: normal;
font-size: 140%;
}
</style>
</head>
<body>
<h1><a href="https://developers.google.com/blockly/">Blockly</a> >
<a href="../index.html">Demos</a> > Step Execution with JS Interpreter</h1>
<p>This is a demo of executing code step-by-step with a sandboxed JavaScript interpreter.</p>
<p>The generator's <code>Blockly.JavaScript.STATEMENT_PREFIX</code> is assigned <code>'highlightBlock(%1);\n'</code>,
where <code>%1</code> is the block id. The call to <code>highlightBlock()</code> will highlight the identified block
and set the variable <code>highlightPause</code> to <code>true</code>.</p>
<p>"Parse JavaScript" will generate the code and load it into the interpreter. Then, each press of the
"Step JavaScript" button will run the interpreter one step until the <code>highlightPause</code> is true.
That is, until <code>highlightBlock()</code> has highlighted the block that will be executed on the next step.</p>
<p>→ <a href="https://developers.google.com/blockly/guides/configure-blockly/web/running-javascript#js_interpreter">More info on running code with JS Interpreter</a></p>
<p>
<button onclick="stepCode()" id="stepButton">Step JavaScript</button>
</p>
<div style="width: 100%">
<div id="blocklyDiv"
style="display: inline-block; height: 480px; width: 58%"></div>
<textarea id="output" disabled="disabled"
style="display: inline-block; height: 480px; width: 38%;">
</textarea>
</div>
<xml xmlns="https://developers.google.com/blockly/xml" id="toolbox" style="display: none">
<category name="Logic" colour="%{BKY_LOGIC_HUE}">
<block type="controls_if"></block>
<block type="logic_compare"></block>
<block type="logic_operation"></block>
<block type="logic_negate"></block>
<block type="logic_boolean"></block>
</category>
<category name="Loops" colour="%{BKY_LOOPS_HUE}">
<block type="controls_repeat_ext">
<value name="TIMES">
<block type="math_number">
<field name="NUM">10</field>
</block>
</value>
</block>
<block type="controls_whileUntil"></block>
</category>
<category name="Math" colour="%{BKY_MATH_HUE}">
<block type="math_number">
<field name="NUM">123</field>
</block>
<block type="math_arithmetic"></block>
<block type="math_single"></block>
</category>
<category name="Text" colour="%{BKY_TEXTS_HUE}">
<block type="text"></block>
<block type="text_length"></block>
<block type="text_print"></block>
<block type="text_prompt_ext">
<value name="TEXT">
<block type="text"></block>
</value>
</block>
</category>
<sep></sep>
<category name="Variables" custom="VARIABLE" colour="%{BKY_VARIABLES_HUE}">
</category>
<category name="Functions" custom="PROCEDURE" colour="%{BKY_PROCEDURES_HUE}">
</category>
</xml>
<xml xmlns="https://developers.google.com/blockly/xml" id="startBlocks" style="display: none">
<block type="variables_set" id="set_n_initial" inline="true" x="20" y="20">
<field name="VAR">n</field>
<value name="VALUE">
<block type="math_number">
<field name="NUM">1</field>
</block>
</value>
<next>
<block type="controls_repeat_ext" id="repeat" inline="true">
<value name="TIMES">
<block type="math_number">
<field name="NUM">4</field>
</block>
</value>
<statement name="DO">
<block type="variables_set" id="set_n_update" inline="true">
<field name="VAR">n</field>
<value name="VALUE">
<block type="math_arithmetic" inline="true">
<field name="OP">MULTIPLY</field>
<value name="A">
<block type="variables_get">
<field name="VAR">n</field>
</block>
</value>
<value name="B">
<block type="math_number">
<field name="NUM">2</field>
</block>
</value>
</block>
</value>
<next>
<block type="text_print" id="print">
<value name="TEXT">
<block type="variables_get">
<field name="VAR">n</field>
</block>
</value>
</block>
</next>
</block>
</statement>
</block>
</next>
</block>
</xml>
<script>
var demoWorkspace = Blockly.inject('blocklyDiv',
{media: '../../media/',
toolbox: document.getElementById('toolbox')});
Blockly.Xml.domToWorkspace(document.getElementById('startBlocks'),
demoWorkspace);
var outputArea = document.getElementById('output');
var stepButton = document.getElementById('stepButton');
var myInterpreter = null;
function initApi(interpreter, globalObject) {
// Add an API function for the alert() block, generated for "text_print" blocks.
interpreter.setProperty(globalObject, 'alert',
interpreter.createNativeFunction(function(text) {
text = arguments.length ? text : '';
outputArea.value += '\n' + text;
}));
// Add an API function for the prompt() block.
var wrapper = function(text) {
return interpreter.createPrimitive(prompt(text));
};
interpreter.setProperty(globalObject, 'prompt',
interpreter.createNativeFunction(wrapper));
// Add an API function for highlighting blocks.
var wrapper = function(id) {
id = String(id || '');
return interpreter.createPrimitive(highlightBlock(id));
};
interpreter.setProperty(globalObject, 'highlightBlock',
interpreter.createNativeFunction(wrapper));
}
var highlightPause = false;
var latestCode = '';
function highlightBlock(id) {
demoWorkspace.highlightBlock(id);
highlightPause = true;
}
function resetStepUi(clearOutput) {
demoWorkspace.highlightBlock(null);
highlightPause = false;
if (clearOutput) {
outputArea.value = 'Program output:\n=================';
}
}
function generateCodeAndLoadIntoInterpreter() {
// Generate JavaScript code and parse it.
Blockly.JavaScript.STATEMENT_PREFIX = 'highlightBlock(%1);\n';
Blockly.JavaScript.addReservedWords('highlightBlock');
latestCode = Blockly.JavaScript.workspaceToCode(demoWorkspace);
resetStepUi(true);
}
function stepCode() {
if (!myInterpreter) {
// First statement of this code.
// Clear the program output.
resetStepUi(true);
myInterpreter = new Interpreter(latestCode, initApi);
// And then show generated code in an alert.
// In a timeout to allow the outputArea.value to reset first.
setTimeout(function() {
alert('Ready to execute the following code\n' +
'===================================\n' + latestCode);
highlightPause = true;
stepCode();
}, 1);
return;
}
highlightPause = false;
do {
try {
var hasMoreCode = myInterpreter.step();
} finally {
if (!hasMoreCode) {
// Program complete, no more code to execute.
outputArea.value += '\n\n<< Program complete >>';
myInterpreter = null;
resetStepUi(false);
// Cool down, to discourage accidentally restarting the program.
stepButton.disabled = 'disabled';
setTimeout(function() {
stepButton.disabled = '';
}, 2000);
return;
}
}
// Keep executing until a highlight statement is reached,
// or the code completes or errors.
} while (hasMoreCode && !highlightPause);
}
// Load the interpreter now, and upon future changes.
generateCodeAndLoadIntoInterpreter();
demoWorkspace.addChangeListener(function(event) {
if (!(event instanceof Blockly.Events.Ui)) {
// Something changed. Parser needs to be reloaded.
generateCodeAndLoadIntoInterpreter();
}
});
</script>
</body>
</html>