1.To sort an array from small to big nums, we can use the following method.
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function compare ( num1 , num2 ){
return num1 - num2 ;
}
var nums = [ 3 , 1 , 2 , 100 , 4 , 200 ];
nums . sort ( compare );
print ( nums );
2.reduce, every, some, forEach迭代器方法
3.map will give out a new array:
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function first ( word ){
return word [ 0 ];
}
var words = [ "for" , "your" , "info" ];
var acronym = words . map ( first );
print ( acronym . join ( "" ));
//fyi
//print(acronym);
//f,y,i
note how we used join to avoid the “,”
4.filter
Filter is quite similar to “every”, it accept a function whose return value is boolean. In contrast to “every”, when filter(func) evaluated to true, it does not retrun “true”, it returns a new array, whose item is the those items in the original way after beed passed to the funcition.
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function passing ( num ) {
return num >= 60 ;
}
var grades = [];
for ( var i = 0 ; i < 20 ; ++ i ) {
grades [ i ] = Math . floor ( Math . random () * 101 );
}
var passGrades = grades . filter ( passing );
print ( grades );
print ( passGrades );
5.the following code shows how to get a studetnt’s average score and how to get a discipline’s averge score.
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//discipline's average score
var grades = [[ 89 , 77 , 78 ],[ 76 , 82 , 81 ],[ 91 , 94 , 89 ]];
var total = 0 ;
var average = 0.0 ;
for ( var col = 0 ; col < grades . length ; ++ col ) {
for ( var row = 0 ; row < grades [ col ]. length ; ++ row ) {
total += grades [ row ][ col ];
}
average = total / grades [ col ]. length ;
print ( "Test " + parseInt ( col + 1 ) + " average: " +
average . toFixed ( 2 ));
total = 0 ;
average = 0.0 ;
}
//a student's average score
var grades = [[ 89 , 77 , 78 ],[ 76 , 82 , 81 ],[ 91 , 94 , 89 ]];
var total = 0 ;
var average = 0.0 ;
for ( var row = 0 ; row < grades . length ; ++ row ) {
for ( var col = 0 ; col < grades [ row ]. length ; ++ col ) {
total += grades [ row ][ col ];
}
average = total / grades [ row ]. length ;
print ( "Student " + parseInt ( row + 1 ) + " average: " +
average . toFixed ( 2 ));
total = 0 ;
average = 0.0 ;
}