简单的 javascript 文件产生 memory 错误

Question

function flipPairs(input){
    var text = '';
    for(var i = 0; i < input.length; i = i + 2){
        text += input[i + 1] + input[i];
    }
    return text;
}


console.log(flipPairs('HI'));

I have this in a file called flipper.js When I run

node flipper.js

I get this error

 node flipper.js

<--- Last few GCs --->

[20506:0x102aac000]    29029 ms: Scavenge 2024.1 (2031.1) -> 2023.8 (2042.3) MB, 9.6 / 0.0 ms  (average mu = 0.272, current mu = 0.259) allocation failure 
[20506:0x102aac000]    29049 ms: Scavenge 2031.3 (2042.3) -> 2032.2 (2043.1) MB, 16.5 / 0.0 ms  (average mu = 0.272, current mu = 0.259) allocation failure 
[20506:0x102aac000]    29069 ms: Scavenge 2032.2 (2043.1) -> 2031.2 (2066.1) MB, 19.8 / 0.0 ms  (average mu = 0.272, current mu = 0.259) allocation failure 


<--- JS stacktrace --->

==== JS stack trace =========================================

    0: ExitFrame [pc: 0x100972e59]
Security context: 0x1a3a9d5008d1 <JSObject>
    1: flipPairs [0x1a3ac10bfe51] [/Users/aneeshakella/Desktop/tests/flipper.js:~1] [pc=0x113893c44259](this=0x1a3ac10bfe31 <JSGlobal Object>,0x1a3a440d5a21 <String[#69]: check out how interesting this problem is, it's insanely interesting!>)
    2: /* anonymous */ [0x1a3ac10bfe91] [/Users/aneeshakella/Desktop/tests/flipper.js:10] [bytecode=0x1a3a440d5ca1 offse...

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory
 1: 0x101018fd1 node::Abort() (.cold.1) [/usr/local/bin/node]
 2: 0x10008632b node::FatalError(char const*, char const*) [/usr/local/bin/node]
 3: 0x10008646c node::OnFatalError(char const*, char const*) [/usr/local/bin/node]
 4: 0x100187727 v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, bool) [/usr/local/bin/node]
 5: 0x1001876c7 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, bool) [/usr/local/bin/node]
 6: 0x100312e75 v8::internal::Heap::FatalProcessOutOfMemory(char const*) [/usr/local/bin/node]
 7: 0x1003146ca v8::internal::Heap::RecomputeLimits(v8::internal::GarbageCollector) [/usr/local/bin/node]
 8: 0x10031114e v8::internal::Heap::PerformGarbageCollection(v8::internal::GarbageCollector, v8::GCCallbackFlags) [/usr/local/bin/node]
 9: 0x10030ef00 v8::internal::Heap::CollectGarbage(v8::internal::AllocationSpace, v8::internal::GarbageCollectionReason, v8::GCCallbackFlags) [/usr/local/bin/node]
10: 0x10030df51 v8::internal::Heap::HandleGCRequest() [/usr/local/bin/node]
11: 0x1002d36f1 v8::internal::StackGuard::HandleInterrupts() [/usr/local/bin/node]
12: 0x1006389ac v8::internal::Runtime_StackGuard(int, unsigned long*, v8::internal::Isolate*) [/usr/local/bin/node]
13: 0x100972e59 Builtins_CEntry_Return1_DontSaveFPRegs_ArgvOnStack_NoBuiltinExit [/usr/local/bin/node]
zsh: abort      node flipper.js

It should be a very simple run. Is there a reason why this is failing. My node version is 12.16.3

Answer 1

the problem is the length of the input, try this:

 function flipPairs(input) { var text = ''; for (var i = 0; i < input.length - 1; i = i + 2) { text += input[i + 1] + input[i]; } return text; } console.log(flipPairs('HI'));

Answer 2

You are trying to call an element that is not listed and an undefined value is returned.

For example;

let array = [1, 2, 3, 4, 5]
for(let i = 0; i < array.length; i = i + 2){
   console.log(array[i + 1])
}

The output here is: 2, 4, undefined

Trying to add an undefined value into the text.