Expose an R vector as a read-only JavaScript view

Creates an array-like JavaScript object that reads directly from retained R vector storage. Creating the view does not copy or convert its elements. Elements are converted only when JavaScript accesses them.

Usage

js_readonly_view(x)

Arguments

x

A raw, logical, integer, double, or character vector.

Value

A lightweight wrapper around the input vector.

Details

The view has length, indexed access, array iteration, and inherited non-mutating Array methods. Use view.toArray() or Array.from(view) when a mutable JavaScript array is required. Attempts to write or delete indexed values throw an error.

The wrapper does not copy the vector. The view retains the wrapper and vector until JavaScript releases them. Normal R assignment follows R's copy-on-write rules, so modifying an R binding can detach it from the storage retained by an existing view. Returning the view to R recovers the wrapper without materialising a JavaScript array.

Missing values use the ordinary conversion rules: logical, integer, double, and character NA become JavaScript null; NaN remains NaN. Factors yield their labels, and dates yield JavaScript dates.

Examples

ctx <- JSContext$new(profile = "bare")
ctx$source(code = paste(
  "function endpoints(x) { return [x[0], x[x.length - 1]]; }",
  "function total(x) { return x.reduce((a, b) => a + b, 0); }"
))
values <- js_readonly_view(as.double(1:1000))
ctx$call("endpoints", values)
#> [1]    1 1000
ctx$call("total", values)
#> [1] 500500