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More realistic custom inspect example #8875

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More realistic custom inspect example #8875

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docs: more realistic custom inspect example
Havvy Oct 1, 2016
ad9ef92
use " ".repeat in custom util.inspect example
Havvy Oct 2, 2016
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30 changes: 24 additions & 6 deletions doc/api/util.md
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Expand Up @@ -286,13 +286,31 @@ invoke and use the result of when inspecting the object:
```js
const util = require('util');

const obj = { name: 'nate' };
obj[util.inspect.custom] = function(depth) {
return `{${this.name}}`;
};
class Box {
constructor(value) {
this.value = value;
}
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I’m not sure, so this is just a suggestion, but maybe leaving the “simpler” example first would be helpful? The Box example is good but maybe a bit overwhelming on the first look?

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If we keep it, then I'd argue that we'd want to also add text saying it's a minimal example.

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@Havvy Agreed. Maybe subheadings that say something like:

A simple example

A more realistic example


util.inspect(obj);
// "{nate}"
inspect(depth, options) {
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@addaleax ... what do you think.. should this be modified to use the new symbol you introduced as an alternative to using inspect directly?

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@jasnell We could do that, but the motivation for introducing the symbol-based alternative were objects that have a regular inspect property which would conflict with what Node expects, and that doesn’t really apply to this use case. And as long as v4.x is supported, just using inspect is probably what I would do here, too. (But yeah, it’s hard to explain that situation concisely in an example).

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@Havvy .. as a suggestion per @fhinkel's request, a code comment in here that describes the basic flow would be helpful.

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Will do when I have time and energy.

if (depth < 0) {
return options.stylize('[Box]', 'special');
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@Havvy ... likewise here, a comment that describes briefly what options.stylize does.

}

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 = util.inspect(this.value, newOptions).replace(/\n/g, '\n' + padding);
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And a comment here about what this call to util.inspect is for.

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Will do when I have time and energy.

return options.stylize('Box', 'special') + '< ' + inner + ' >';
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@jasnell jasnell Oct 6, 2016 •
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I know I already signed off on this but, just as a very minor nit, this could be slightly simplified to:

return `${options.stylize('Box', 'special')}<${inner}>`;

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I am not sure I’d find that more readable… long expressions inside ${} are a bit weird imho.

So, maybe options.stylize('Box', 'special') + < ${inner} >;?

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Do we really want to mix quasiquoting and string concatenation together?

Seems like any option we go with (other than just string concatenation IMO) looks weird.

}
}

const box = new Box(true);

util.inspect(box);
// "Box< true >"
```

Custom `[util.inspect.custom](depth, opts)` functions typically return a string
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