Properties

Use template.properties to read/write properties:

```pochoir-js
template.properties.author = "John Do";
```

Output:

---
author: "John Do"
---

Alternatively, you can use $.properties property.

The frontmatter builder

Use template.$properties for more complex use case, like inserting tag to tags property:

```pochoir-js
template.$properties.insertTo("tags", "bookmark");
```

Output:

---
tags:
- bookmark
---

Full example

// Set property
template.$properties.set("author", "John Doe");

// Remove property
template.$properties.delete("author", "John Doe");

// Add bookmark to the list `tags`
template.$properties.insertTo("tags", "bookmark");

// Remove bookmark to the list `tags`
template.$properties.removeTo("tags", "bookmark");

// Get list `tags` (returns string[])
const tags = template.$properties.list("tags");
console.log(tags);

// Remove all properties
template.$properties.clear();

// Merge with an object
template.$propertes.merge({
    author: "John Doe",
    tags: ["bookmark"]
});

// Merge yaml string
template.$properties.merge(`
author: John Doe
tags:
- bookmark
`);

// Clone properties
const cloned = template.$properties.clone();
cloned.set("age", "34");

// Merge with another PropertyBuilder
template.$properties.merge(cloned);

// Get an object (returns Record<string, unknown>)
const properties = template.$properties.toObject();

// Get a yaml string (returns string)
const yaml = template.$properties.toYAML();

Merge properties from another template

Sometime you want to insert properties from a template to another one. There's multiple way to do that, but first we will expose the wrong way with the following example.

We have two templates [[Template 1]] and [[Template 2]]:

With [[Template 1]], a function createdAt is exported. This function inserts created-at property:

```pochoir-js
const { today } = await template.import("pochoir:date");
template.exports.createdAt = () => {
    template.properties["created-at"] = today('YYYY-MM-DD');
};
```

And we use createdAt in [[Template 2]]:

```pochoir-js
const { createdAt } = await template.import("[[Template 1]]");
createdAt();
```

You may expect this result, but this is not the case:

---
created-at: 2025-07-23
---

Because template.properties in [[Template 1]] does not belong to [[Template 2]] context but the former.

You need to provide [[Template 2]] properties object:

```pochoir-js
const { today } = await template.import("pochoir:date");
template.exports.createdAt = (properties) => { // 👈
    properties["created-at"] = today('YYYY-MM-DD'); // 👈
};
```

```pochoir-js
const { createdAt } = await template.import("[[Template 1]]");
createdAt(template.properties); // 👈
```

An alternative way would be to expose an object

```pochoir-js
const { today } = await template.import("pochoir:date");
template.exports.properties = {
    get ["created-at"]() {
        return today("YYYY-MM-DD"):
    },
}; // 👈
```

```pochoir-js
const { properties } = await template.import("[[Template 1]]");
template.$properties.merge(properties); // 👈
```

Or to expose a more exportable function:

```pochoir-js
const { today } = await template.import("pochoir:date");
template.exports.createdAt = () => today('YYYY-MM-DD'); // 👈
```

```pochoir-js
const { createdAt } = await template.import("[[Template 1]]");
template.properties["created-at"] = createdAt(); // 👈
```