yodaos-project/ShadowNode

jerry: does not support String.prototype.startsWith()

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#472 opened on Dec 28, 2018

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good first issuejerry

Description

ES6又提供了三种新方法。

includes()：返回布尔值，表示是否找到了参数字符串。

startsWith()：返回布尔值，表示参数字符串是否在源字符串的头部。

endsWith()：返回布尔值，表示参数字符串是否在源字符串的尾部。

请支持。

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Contributor guide

Tech stack
javascript
Domain
api
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C programmingJerryScript internalsECMAScript specification
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
First, locate the JerryScript source code in the ShadowNode repository (likely in the `deps/jerry` directory). Examine how existing String prototype methods like `includes` are implemented in `jerry core/ecma/operations/ecma string object.c` or similar. The ECMAScript 6 specification for `String.prototype.startsWith` (section 21.1.3.6) defines the algorithm: check if `searchString` is a regex (throw TypeError), coerce `this` to string, compute position, and then compare substrings. Follow the pattern of existing implementations, handling ToString, ToInteger, and string length checks. Ensure the method is added to the builtin list and exported. Look at prior commits or PRs for guidance on adding new built in methods.