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inspect.js
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inspect.js
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/**
* Copyright (c) 2015-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow strict
*/
import nodejsCustomInspectSymbol from './nodejsCustomInspectSymbol';
/**
* Used to print values in error messages.
*/
export default function inspect(value: mixed): string {
switch (typeof value) {
case 'string':
return JSON.stringify(value);
case 'function':
return value.name ? `[function ${value.name}]` : '[function]';
case 'object':
if (value) {
const customInspectFn = getCustomFn(value);
if (customInspectFn) {
// $FlowFixMe(>=0.90.0)
const customValue = customInspectFn.call(value);
return typeof customValue === 'string'
? customValue
: inspect(customValue);
} else if (Array.isArray(value)) {
return '[' + value.map(inspect).join(', ') + ']';
}
const properties = Object.keys(value)
.map(k => `${k}: ${inspect(value[k])}`)
.join(', ');
return properties ? '{ ' + properties + ' }' : '{}';
}
return String(value);
default:
return String(value);
}
}
function getCustomFn(object) {
const customInspectFn = object[String(nodejsCustomInspectSymbol)];
if (typeof customInspectFn === 'function') {
return customInspectFn;
}
if (typeof object.inspect === 'function') {
return object.inspect;
}
}