TMPA-2017: Static Checking of Array Objects in JavaScript
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The document discusses the conventionality of JavaScript arrays, exploring their properties and usage compared to conventional programming languages. It highlights the importance of conventionality analysis for program comprehension and performance optimization, noting that most JavaScript arrays are predominantly used in conventional ways. The authors propose integrating conventionality analysis into static analyzers and suggest future work focusing on performance optimization using array information.
![var A = [ ] ; / New empty array /
var i ;
function populate_array (x,y,A) {
for (i=x ; i<=y ; i++) {
A[i]= 2*i +10;
}
return A;
}
A = populate_array (0, 3, A) ;
A = populate_array (6, 10, A) ;
A.prop1 = “foo” ;
i= -3.5; A[i] = true;
[0, 3] [10,16], [6,10] [22,30], // A has indexes 0—3, 6—10
// A is not dense
“prop1” “foo”,
SNum true // A is not conventional
“length” 11](https://image.slidesharecdn.com/12-50lu-tmpa-2017-170323080844/85/TMPA-2017-Static-Checking-of-Array-Objects-in-JavaScript-5-320.jpg)
TMPA-2017: Static Checking of Array Objects in JavaScript
- 1. Astrid Younang & Lunjin Lu & Nabil Almashfi March 3,2017
- 2. Outline 1. Motivation 2. Related Work 3. Conventionality Analysis 4. Conclusion and Future Work
- 3. Motivation JavaScript objects have dynamic set of fields (properties) Arrays are just like regular objects with the property (field) length that is automatically updated; Arrays can have fields whose names are not indices; Are they used like regular objects? Are they used in a conventional way like in Java ?
- 4. Motivation A conventional array is an array that does not have any properties other than indices and length. Conventionality analysis • provides valuable information for program comprehension • provides valuable information for performance optimization • Feature to add to JavaScript development tool
- 5. var A = [ ] ; / New empty array / var i ; function populate_array (x,y,A) { for (i=x ; i<=y ; i++) { A[i]= 2*i +10; } return A; } A = populate_array (0, 3, A) ; A = populate_array (6, 10, A) ; A.prop1 = “foo” ; i= -3.5; A[i] = true; [0, 3] [10,16], [6,10] [22,30], // A has indexes 0—3, 6—10 // A is not dense “prop1” “foo”, SNum true // A is not conventional “length” 11
- 6. Information tracked by conventional analysis String information: what strings a variable can take as value? Number information: what numbers a variable can take as a value? Type information: is a number definitely integer or possibly a floating point number?
- 7. Related Work Existing abstract string domains Constant propagation domain for strings (TAJS, SAFE, JSAI) Character inclusion, prefix domain, suffix domain, bricks and string graphs Automata-based string domains
- 8. Related Work Existing abstract string domains do not track range of indexes (which are strings) precisely do not supports conventionality analysis
- 10. Abstract string domain- Operations n – a non-index numeric string r – a non-numeric string
- 11. Abstract numeric domain Range -- Interval domain intv(3,5) – all numbers between 3 and 5 norm(3,5) – all numbers between 3 and d plus NaN Type -- <int, any>
- 12. Evaluation Studied 98 benchmark programs 70 out of them had less than 2 arrays (were omitted)
- 13. Evaluation
- 14. Evaluation Only conventional arrays were found on GitHub o Programmers most likely use arrays in a conventional way and flagging possible non-conventional arrays provides useful information during program development.
- 15. Evaluation Arrays are used in a conventional way in 95% of the benchmark programs. Storage of single/mixed types o 377 arrays analyzed o 11.93% - string values o 33% - integer values
- 16. Conclusion & Future work Conventionality analysis can be integrated in static analyzers Future work will investigate the use the use of array information for performance optimization