116 lines
2.5 KiB
JavaScript
116 lines
2.5 KiB
JavaScript
const MAX_ARRAY_LENGTH = 10;
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const MAX_RECURSIVE_DEPTH = 2;
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/**
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* Used to print values in error messages.
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*/
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export function inspect(value) {
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return formatValue(value, []);
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}
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function formatValue(value, seenValues) {
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switch (typeof value) {
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case 'string':
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return JSON.stringify(value);
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case 'function':
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return value.name ? `[function ${value.name}]` : '[function]';
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case 'object':
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return formatObjectValue(value, seenValues);
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default:
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return String(value);
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}
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}
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function formatObjectValue(value, previouslySeenValues) {
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if (value === null) {
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return 'null';
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}
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if (previouslySeenValues.includes(value)) {
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return '[Circular]';
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}
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const seenValues = [...previouslySeenValues, value];
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if (isJSONable(value)) {
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const jsonValue = value.toJSON(); // check for infinite recursion
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if (jsonValue !== value) {
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return typeof jsonValue === 'string'
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? jsonValue
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: formatValue(jsonValue, seenValues);
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}
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} else if (Array.isArray(value)) {
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return formatArray(value, seenValues);
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}
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return formatObject(value, seenValues);
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}
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function isJSONable(value) {
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return typeof value.toJSON === 'function';
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}
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function formatObject(object, seenValues) {
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const entries = Object.entries(object);
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if (entries.length === 0) {
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return '{}';
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}
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if (seenValues.length > MAX_RECURSIVE_DEPTH) {
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return '[' + getObjectTag(object) + ']';
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}
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const properties = entries.map(
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([key, value]) => key + ': ' + formatValue(value, seenValues),
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);
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return '{ ' + properties.join(', ') + ' }';
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}
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function formatArray(array, seenValues) {
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if (array.length === 0) {
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return '[]';
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}
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if (seenValues.length > MAX_RECURSIVE_DEPTH) {
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return '[Array]';
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}
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const len = Math.min(MAX_ARRAY_LENGTH, array.length);
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const remaining = array.length - len;
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const items = [];
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for (let i = 0; i < len; ++i) {
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items.push(formatValue(array[i], seenValues));
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}
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if (remaining === 1) {
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items.push('... 1 more item');
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} else if (remaining > 1) {
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items.push(`... ${remaining} more items`);
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}
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return '[' + items.join(', ') + ']';
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}
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function getObjectTag(object) {
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const tag = Object.prototype.toString
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.call(object)
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.replace(/^\[object /, '')
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.replace(/]$/, '');
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if (tag === 'Object' && typeof object.constructor === 'function') {
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const name = object.constructor.name;
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if (typeof name === 'string' && name !== '') {
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return name;
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}
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}
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return tag;
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}
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