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Primer

Module Expressions

parse(expression)

Parse an expression.
This returns a JSON that contains a list of query parts, and methods for interacting with the query.
Arguments
  • expression { Expression } Any valid expression.
const expressions = require('expressions')
return expressions.parse({
$toString: '$NOW'
})
Returns
  • { * } The ran expression.
{
"object": "result",
"data": {
"depth": 1,
"fullPath": "$toString",
"input": {
"$toString": "$NOW"
},
"path": "$toString",
}}

run(expression, root)

This runs the command in the context of the current database.
Arguments
  • expression { Expression } Any valid expression.
const expressions = require('expressions')
return expressions.run({
$toString: '$NOW'
})
Returns
  • { * } The ran expression.
{
"object": "result",
"data": "Wed Oct 07 2020 16:14:16 GMT+0000 (Coordinated Universal Time)"
}

evaluate(expression, root)

This evaluates an expression, running the expression and returning a JSON that contains a list of query parts, and methods for interacting with the query. Arguments
  • expression { Expression } Any valid expression.
const expressions = require('expressions')
return expressions.evaluate({
$toString: '$NOW'
})
Returns
  • { * } The ran expression.
{
"object": "result",
"data": {
"accessScope": {
"allow": 0,
"context": {
"object": ""
},
"grant": 0,
"instanceRoles": [],
"object": "ac",
"org": {
...}
}
}
}

Pipelines

Pipeline aggregation allows for querying, aggregating, and transforming data in multiple stages in real-time through a single API request. While query arguments allow for making simple, single-stage queries through the API, pipelines allow for more complex searches, aggregations and transformations.

pipeline.parse(expression)

This returns a JSON that contains a list of query parts, and methods for interacting with the query.
Arguments
  • expression { Expression } Any valid expression.
const expressions = require('expressions')
return expressions.parse({
$toString: '$NOW'
})
Returns
  • { * } The ran expression.
{
"object": "result",
"data": {
"depth": 1,
"fullPath": "$toString",
"input": {
"$toString": "$NOW"
},
"path": "$toString",
"type": "Expression$operator",
"value": {
"expression": {
...
}
}
}
}

pipeline.run(expression, input)

This runs the command in the context of the current database.
Arguments
  • expression { Expression } Any valid expression.
const expressions = require('expressions')
return expressions.pipeline.run([
{
$project: { $split: ['$ROOT', ' '] }
}
],
['This is a test', 'we are testing pipelines', 'Medable is cool']
).toArray()
Returns
  • { * } The ran expression.
{
"data": [
[
"This",
"is",
"a",
"test"
],
[
"We",
"are",
"testing",
"pipelines"
],
[
"Medable",
"is",
"cool"
]
],
"hasMore": false,
"object": "list"
}
Arguments
  • expression { Expression } Any valid expression.
  • input { Array|Cursor = null } An array or cursor to serve as initial input.

pipeline.evaluate(expression, input)

This evaluates an expression, running the expression and returning a JSON that contains a list of query parts, and methods for interacting with the query.
Arguments
  • expression { Expression } Any valid expression.
const expressions = require('expressions')
return expressions.pipeline.evaluate([
{
$project: { $split: ['$ROOT', ' '] }
}
],
['This is a message', 'Pipelines are being tested', 'Sky is blue']
)
Returns
  • { * } The evaluated expression.
{
"object": "result",
"data": {
"accessScope": {
"allow": 0,
"context": {
"object": ""
},
"grant": 0,
}}}
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On this page
Module Expressions
parse(expression)
run(expression, root)
evaluate(expression, root)
Pipelines
pipeline.parse(expression)
pipeline.run(expression, input)
pipeline.evaluate(expression, input)