对象上的自定义检查函数
对象也可以定义自己的 [util.inspect.custom](depth, opts, inspect)
函数,util.inspect()
将在检查对象时调用并使用其结果。
const util = require('node:util');
class Box {
constructor(value) {
this.value = value;
}
[util.inspect.custom](depth, options, inspect) {
if (depth < 0) {
return options.stylize('[Box]', 'special');
}
const newOptions = Object.assign({}, options, {
depth: options.depth === null ? null : options.depth - 1,
});
// 五个空格填充,因为这是“Box<”的大小。
const padding = ' '.repeat(5);
const inner = inspect(this.value, newOptions)
.replace(/\n/g, `\n${padding}`);
return `${options.stylize('Box', 'special')}< ${inner} >`;
}
}
const box = new Box(true);
util.inspect(box);
// 返回: "Box< true >"
自定义的 [util.inspect.custom](depth, opts, inspect)
函数通常返回一个字符串,但也可能返回一个由 util.inspect()
相应格式化的任何类型的值。
const util = require('node:util');
const obj = { foo: 'this will not show up in the inspect() output' };
obj[util.inspect.custom] = (depth) => {
return { bar: 'baz' };
};
util.inspect(obj);
// 返回: "{ bar: 'baz' }"
Objects may also define their own
[util.inspect.custom](depth, opts, inspect)
function,
which util.inspect()
will invoke and use the result of when inspecting
the object.
const util = require('node:util');
class Box {
constructor(value) {
this.value = value;
}
[util.inspect.custom](depth, options, inspect) {
if (depth < 0) {
return options.stylize('[Box]', 'special');
}
const newOptions = Object.assign({}, options, {
depth: options.depth === null ? null : options.depth - 1,
});
// Five space padding because that's the size of "Box< ".
const padding = ' '.repeat(5);
const inner = inspect(this.value, newOptions)
.replace(/\n/g, `\n${padding}`);
return `${options.stylize('Box', 'special')}< ${inner} >`;
}
}
const box = new Box(true);
util.inspect(box);
// Returns: "Box< true >"
Custom [util.inspect.custom](depth, opts, inspect)
functions typically return
a string but may return a value of any type that will be formatted accordingly
by util.inspect()
.
const util = require('node:util');
const obj = { foo: 'this will not show up in the inspect() output' };
obj[util.inspect.custom] = (depth) => {
return { bar: 'baz' };
};
util.inspect(obj);
// Returns: "{ bar: 'baz' }"