Conditional operators

Operators used to perform conditional operations.

$cond

Evaluates a boolean expression and based on the result, returns one of the two specified return expressions.

{ "$cond": { "if": "boolean", "then": "any", "else": "any" } }

expry({ $cond: { if: true, then: "yes", else: "no" } }); // "yes"
expry({ $cond: { if: false, then: "yes", else: "no" } }); // "no"

$ifNull

Returns the first non-null expression, or null if all expressions are null.

{ "$ifNull": ["any", "any", "...", "replacement"] }

expry({ $ifNull: [null, "hello", "bye"] }); // "hello"
expry({ $ifNull: [null, null, "bye"] }); // "bye"
expry({ $ifNull: [null, null, null] }); // null
expry({ $ifNull: [] }); // null

$switch

Evaluates a series of case expressions and returns the value of the first expression that evaluates to true, or the default value if there is no expression that evaluates to true.

{
  "$switch": {
    "branches": [
      { "case": "boolean", "then": "any" },
      { "case": "boolean", "then": "any" }
      "..."
    ],
    "default": "any"
  }
}

expry({
  $switch: {
    branches: [
      { case: false, then: 1 },
      { case: true, then: 2 },
    ],
    default: 3,
  },
}); // 2
expry({
  $switch: {
    branches: [
      { case: false, then: 1 },
      { case: false, then: 2 },
    ],
    default: 3,
  },
}); // 3