defineTreeProjection

KIT · function · 运行时值

Compile a depth-limited tree transform.

Traverse synchronously in property/array order; only undefined omits a result. Because a visitor returns a new value instead of mutating, an omitted branch disappears from arrays and objects the same way, and maxDepth bounds both cycles and cost.

导入

TypeScript

import { defineTreeProjection } from '@jangts/agent-core/kits/projection';

JavaScript

import { defineTreeProjection } from '@jangts/agent-core/kits/projection';

其他公开入口：@jangts/agent-core/types、@jangts/agent-core/kits/projection、@jangts/agent-core/kits。

定义

泛型参数

类型参数	约束	默认类型
Context	—	—

调用

defineTreeProjection<Context>(options: TreeProjectionOptions<Context>): Readonly<{ visit: (value: unknown, context: Context) => unknown; }>

Compile a depth-limited tree transform.

Traverse synchronously in property/array order; only undefined omits a result. Because a visitor returns a new value instead of mutating, an omitted branch disappears from arrays and objects the same way, and maxDepth bounds both cycles and cost.

类型参数	约束	默认类型
Context	—	—

参数	类型	传递	说明
options	TreeProjectionOptions<Context>	必需	—

options 的字段

字段	类型	必需	说明
maxDepth	number	必需	只读。Maximum included depth; deeper values are omitted. Must be a non-negative integer.
omit	((value: unknown, depth: number, context: Context) => boolean) | undefined	可省略	只读。Drops a value when it returns true; must be synchronous boolean.
visitRecord	((value: Record<string, unknown>, depth: number, context: Context) => void) | undefined	可省略	只读。Observes every retained record, for example to record which fields were kept.

返回： Readonly<{ visit: (value: unknown, context: Context) => unknown; }>。

返回值结构

字段	类型	必需	说明
visit	(value: unknown, context: Context) => unknown	必需	见类型定义及调用场景。

使用示例

• Projection：按预算投影内容：先缩短文本，再减少条目；源数据、投影结果和预算由 App 显式区分。

为同一份查询结果准备紧凑 JSON

入门 · Node.js

TypeScript

import { Projection } from '@jangts/agent-core/kits/projection';
const projection = Projection.defineContentProjection({
  counts: [10, 3, 1], lengths: [200, 80, 20],
  render: value => JSON.stringify(value), fallback: () => '{}',
});
const result = projection.project({ value: { items: [{ title: '配置说明', body: '正文'.repeat(100) }] }, maxChars: 120 });
console.log(result.text, result.truncated);

JavaScript

import { Projection } from '@jangts/agent-core/kits/projection';
const projection = Projection.defineContentProjection({
    counts: [10, 3, 1], lengths: [200, 80, 20],
    render: value => JSON.stringify(value), fallback: () => '{}',
});
const result = projection.project({ value: { items: [{ title: '配置说明', body: '正文'.repeat(100) }] }, maxChars: 120 });
console.log(result.text, result.truncated);

相同数据先移除私有字段，再按预算投影

配置 · Node.js

TypeScript

import { Projection } from '@jangts/agent-core/kits/projection';
const tree = Projection.defineTreeProjection({
  maxDepth: 4,
  visitRecord(record) { delete record.privateNote; },
});
const source = { items: [{ title: '配置说明', body: '正文'.repeat(100), privateNote: '不向模型提供' }] };
// 调用者明确选择副本所有权；visitor 不会碰原记录。
const publicData = tree.visit(structuredClone(source), undefined);
const compact = Projection.defineContentProjection({ counts: [10, 3, 1], lengths: [200, 80, 20], render: JSON.stringify, fallback: () => '{}' });
console.log(compact.project({ value: publicData, maxChars: 120 }));

JavaScript

import { Projection } from '@jangts/agent-core/kits/projection';
const tree = Projection.defineTreeProjection({
    maxDepth: 4,
    visitRecord(record) { delete record.privateNote; },
});
const source = { items: [{ title: '配置说明', body: '正文'.repeat(100), privateNote: '不向模型提供' }] };
// 调用者明确选择副本所有权；visitor 不会碰原记录。
const publicData = tree.visit(structuredClone(source), undefined);
const compact = Projection.defineContentProjection({ counts: [10, 3, 1], lengths: [200, 80, 20], render: JSON.stringify, fallback: () => '{}' });
console.log(compact.project({ value: publicData, maxChars: 120 }));

保留连续正文而非拆散段落

扩展 · Node.js

render 的输出长度须随前缀长度单调增长，二分搜索才有意义。

TypeScript

import { Projection } from '@jangts/agent-core/kits/projection';
const body = '一段连续的资料正文。'.repeat(100);
const excerpt = Projection.projectContinuousExcerpt(body, 120, length => JSON.stringify({ excerpt: body.slice(0, length) }));
if (excerpt) console.log(JSON.parse(excerpt.text));

JavaScript

import { Projection } from '@jangts/agent-core/kits/projection';
const body = '一段连续的资料正文。'.repeat(100);
const excerpt = Projection.projectContinuousExcerpt(body, 120, length => JSON.stringify({ excerpt: body.slice(0, length) }));
if (excerpt)
    console.log(JSON.parse(excerpt.text));

相关策略源码

• 缩减顺序与树遍历

相关定义

• TreeProjectionOptions