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Pipeline Terminator - Iteration

In this section, we’ll explore how to use iteration terminators in Pipeline. We’ll use items model for this example.

var schema = {
    id: {
        type: NIMBUSDB_DATA_TYPE.INTEGER,
        const: NIMBUSDB_CONSTRAINT.PRIMARY_KEY
    },
    name: NIMBUSDB_DATA_TYPE.STRING,
    price: {
        type: NIMBUSDB_DATA_TYPE.NUMBER,
        validator: function(data, value) {
            return value >= 0;
        },
        default_value: 0
    },
    is_locked: {
        type: NIMBUSDB_DATA_TYPE.BOOLEAN,
        const: NIMBUSDB_CONSTRAINT.OPTIONAL,
        default_value: false
    }
};


items = new NimbusDBModel("global", "items", schema, [
    { id: 1, name: "Apple", price: 5 },
    { id: 2, name: "Banana", price: 7.2 },
    { id: 3, name: "Cherry", price: 15 },
    { id: 4, name: "Date", price: 12.5 },
    { id: 5, name: "Elderberry", price: 8 },
    { id: 6, name: "Fig", price: 10 },
    { id: 7, name: "Grape", price: 6 },
    { id: 8, name: "Honeydew", price: 9 },
    { id: 9, name: "Kiwi", price: 4 },
    { id: 10, name: "Lemon", price: 3 }
]);

Iteration

Section titled “Iteration”

Foreach Any

Section titled “Foreach ”

The foreach terminator iterates over each element in the pipeline and executes a function on each element.

var items_pl = items.pipe().isolate()
    .filter(function(data, index) {     // include only items with `price` greater than or equal to 8
        return data.price >= 8;
    })
    .limit(3)                           // limit the result to 3 items
    .map(function(data, index) {        // map the result to an array of strings
        return data.name;
    });


var result = items_pl.foreach(function(data, index) {
    show_debug_message($"Item {index + 1}: {data}");
});


// Item 1: Cherry
// Item 2: Date
// Item 3: Elderberry

Reduce Any

Section titled “Reduce ”

The reduce terminator iterates over each element in the pipeline and reduces the result to a single value using a reducer function.

var items_pl = items.pipe().isolate()
    .filter(function(data, index) {     // include only items with `price` greater than or equal to 8
        return data.price >= 8;
    })
    .limit(3)                           // limit the result to 3 items
    .map(function(data, index) {        // map the result to an array of numbers
        return data.price;
    });


var result = items_pl.reduce(function(acc, data, index) {
    acc.total_price += data;
    return acc;
}, {
    total_price: 0
});
show_debug_message($"Total price: {result.total_price}");


// Total price: 35.5

References

Section titled “References”

Pipeline.foreach()

Section titled “Pipeline.foreach()”

Executes the pipeline and iterates over each element in the result.

Signature

Section titled “Signature”
pipeline.d.ts
class NimbusDBPipeline {
    // ... other methods and properties ...
    static foreach(
        _func:
            | ((element: any, index: int) => void)  // array
            | ((prop: string, value: any) => void)  // object
            | ((result: any) => void),              // non-array or object
        _options?: NimbusDBPipelineTerminalOptions
    ): void;
}

Parameters

Section titled “Parameters”
_func
Section titled “_func”
  • Type: (element: any, index: int) => void | (prop: string, value: any) => void | (result: any) => void
    • Parameters:
      • element: The current data element.
      • index: The current index.
      • prop: The current property name.
      • value: The current property value.
      • result: The current result.
    • Returns: void
  • The function to use to iterate over the result.
_options
Section titled “_options”
  • Type: NimbusDBPipelineTerminalOptions
  • Default: undefined
  • An optional object that allows you to customize the behavior of the foreach operation.

Returns

Section titled “Returns”
  • Type: void

Pipeline.reduce()

Section titled “Pipeline.reduce()”

Executes the pipeline and reduces the result to a single value using a reducer function.

Signature

Section titled “Signature”
pipeline.d.ts
class NimbusDBPipeline {
    // ... other methods and properties ...
    static reduce(
        _func:
            | ((acc: any, element: any, index: int) => any)  // array
            | ((acc: any, prop: string, value: any) => any)  // object
            | ((acc: any, result: any) => any),              // non-array or object
        _acc?: any,
        _options?: NimbusDBPipelineTerminalOptions
    ): any;
}

Parameters

Section titled “Parameters”
_func
Section titled “_func”
  • Type: (acc: any, element: any, index: int) => any | (acc: any, prop: string, value: any) => any | (acc: any, result: any) => any
    • Parameters:
      • acc: The current accumulator.
      • element: The current element.
      • index: The current index.
    • Returns: The reduced value.
  • The function to use to reduce the result.
_acc
Section titled “_acc”
  • Type: any
  • Default: undefined
  • The initial accumulator value.
_options
Section titled “_options”
  • Type: NimbusDBPipelineTerminalOptions
  • Default: undefined
  • An optional object that allows you to customize the behavior of the reduce operation.

Returns

Section titled “Returns”
  • Type: any
  • The reduced value.