treehouse/static/js/components/literate-programming/eval.js

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let outputIndex = 0;
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export const jsConsole = console;
// Overwrite globalThis.console with domConsole to redirect output to the DOM console.
// To always output to the JavaScript console regardless, use jsConsole.
export const domConsole = {
log(...message) {
postMessage({
kind: "output",
output: {
kind: "console.log",
message: [...message],
},
outputIndex,
});
}
};
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async function withTemporaryGlobalScope(callback) {
let state = {
oldValues: {},
set(key, value) {
this.oldValues[key] = globalThis[key];
globalThis[key] = value;
}
};
await callback(state);
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jsConsole.trace(state.oldValues, "bringing back old state");
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for (let key in state.oldValues) {
globalThis[key] = state.oldValues[key];
}
}
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let evaluationComplete = null;
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export async function evaluate(commands, { error, newOutput }) {
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if (evaluationComplete != null) {
await evaluationComplete;
}
let signalEvaluationComplete;
evaluationComplete = new Promise((resolve, _reject) => {
signalEvaluationComplete = resolve;
})
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outputIndex = 0;
try {
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for (let command of commands) {
if (command.kind == "module") {
let blobUrl = URL.createObjectURL(new Blob([command.source], { type: "text/javascript" }));
let module = await import(blobUrl);
for (let exportedKey in module) {
globalThis[exportedKey] = module[exportedKey];
}
} else if (command.kind == "output") {
if (newOutput != null) {
newOutput(outputIndex);
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}
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++outputIndex;
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}
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}
postMessage({
kind: "evalComplete",
});
} catch (err) {
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postMessage({
kind: "output",
output: {
kind: "error",
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message: [err.toString()],
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},
outputIndex,
});
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if (error != null) {
error();
}
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}
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signalEvaluationComplete();
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}