mapEach

Commentary

added in 0.7.16

Applies function to each element in the array over.

Optionally, specify juxt to juxtapose a series of key paths before function is applied. ¹

---

Examples

Applying a function

Use function to apply a function to each element in the array. To access the element, reference the reserved variable mapItem. This variable is only allowed in the context of a mapped function.

{
    "_gen": "mapEach",
    "over": [
        0,
        0.25,
        0.5,
        0.75,
        1
    ],
    "function": {
        "_gen": "sin",
        "degrees": {
            "_gen": "var",
            "var": "mapItem"
        }
    }
}

[
    [
        0,
        0.004363309284746571,
        0.008726535498373935,
        0.013089595571344441,
        0.01745240643728351
    ]
]

Juxtaposing paths

You can optionally specify juxt, which is an array of paths. This is useful for picking apart composite objects into an array of values, and then applying function to the resulting array.

This example sums the total value of a shopping cart, where the cart contains items with prices and quantities.

juxt extracts the price and quantity in each item, applies the multiply function, then passes the resulting array to add to sum up the final value.

{
    "_gen": "add",
    "args": {
        "_gen": "mapEach",
        "over": {
            "_gen": "repeatedly",
            "n": 3,
            "target": {
                "price": {
                    "_gen": "uniformDistribution",
                    "bounds": [
                        5,
                        16
                    ],
                    "decimals": 2
                },
                "quantity": {
                    "_gen": "uniformDistribution",
                    "bounds": [
                        1,
                        5
                    ],
                    "decimals": 0
                }
            }
        },
        "juxt": [
            [
                "price"
            ],
            [
                "quantity"
            ]
        ],
        "function": {
            "_gen": "multiply",
            "args": {
                "_gen": "var",
                "var": "mapItem"
            }
        }
    }
}

[
    72.38,
    110.37,
    70.33,
    107.19,
    60.21
]

---

Specification

JSON schema

{
    "type": "object",
    "properties": {
        "over": {
            "oneOf": [
                {
                    "type": "array"
                },
                {
                    "type": "object",
                    "properties": {
                        "_gen": {
                            "type": "string"
                        }
                    },
                    "required": [
                        "_gen"
                    ]
                }
            ]
        },
        "juxt": {
            "type": "array",
            "items": {
                "type": "array",
                "items": {
                    "oneOf": [
                        {
                            "type": "integer",
                            "minimum": 0
                        },
                        {
                            "type": "string"
                        }
                    ]
                }
            }
        },
        "function": {
            "type": "object",
            "properties": {
                "_gen": {
                    "type": "string"
                }
            },
            "required": [
                "_gen"
            ]
        }
    },
    "required": [
        "over",
        "function"
    ]
}