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This article covers features introduced in SpiderMonkey 17

Convert any JavaScript value to a double.


JS::ToNumber(JSContext *cx, JS::HandleValue v, double *out);
Name Type Description
cx JSContext * The context in which to perform the conversion. Requires request. In a JS_THREADSAFE build, the caller must be in a request on this JSContext.
v JS::HandleValue The value to convert.
out double * Out parameter. On success, *out receives the converted floating-point value.


JS::ToNumber converts a JavaScript value to a number. It implements the ToNumber operator described in ECMA 262-3 §9.3.

On success, JS::ToNumber stores the converted value in *out and returns true. On error or exception, it returns false, and the value left in *out is undefined.

See Also