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#199 — define function length property value for default-value and rest parameters

• bug_id: 199
• creation_ts: 2011-08-30 10:31:00 -0700
• short_desc: define function length property value for default-value and rest parameters
• delta_ts: 2013-10-28 16:43:09 -0700
• product: Draft for 6th Edition
• component: new feature
• version: Rev 2: July 25, 2011 Draft
• rep_platform: All
• op_sys: All
• bug_status: RESOLVED
• resolution: FIXED
• priority: Normal
• bug_severity: enhancement
• everconfirmed: true
• reporter: Allen Wirfs-Brock
• assigned_to: Allen Wirfs-Brock
• flag: {"_attributes"=>{"name"=>"TC39Review", "id"=>"6", "type_id"=>"1", "status"=>"?", "setter"=>"allen"}}

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• commentid: 423
• comment_count: 0
• who: Allen Wirfs-Brock
• bug_when: 2011-08-30 10:31:50 -0700

The most reasonable definition seems to be:

The number of parameter positions (including the rest parameter if specified) that precede the first default-value parameter (or the end of the list if there are no default-value parameters):
function (a,b,c) {} //length==3
function (a,b,...c) {} //length==3
function (...c) {} // length=1
function (a=1,b=2) {} //length==0
function (a,b=1) {} //length==1
function (a,b=1,...c) {} //length==1

This treats rest as meaning "usually at least one" (unless following a default-value parameter) which seems to be the way open-ended parameter lists were interpreted in assigning length to most such Chapter 15 functions. I think that this rule would yield the most matches with the specified lengths of chapter 15 functions when their signatures are rewritten using default-value and rest parameter notation.

See thread starting at https://mail.mozilla.org/pipermail/es-discuss/2011-August/016361.html

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• commentid: 6014
• comment_count: 1
• who: Allen Wirfs-Brock
• bug_when: 2013-10-28 16:43:09 -0700

this was settle a long time ago