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@daveyerwinDec 05.2021 — #Javascript concurrency, threading and synchronicity
are not responsible for the results of the code
you posted.
try this script ...
when copyOfPerson's name property was changed
person's name property was also changed!
WHY?
because both copyOfPerson and person both REFER to the SAME object
https://codeburst.io/explaining-value-vs-reference-in-javascript-647a975e12a0 @daveyerwinDec 05.2021 — #
Javascript Threads – Confusing
If I run the following code:
let data = []
person = {}
person[“name”] = “Bob”
person[“age”] = 30
person[“skills”] = {}
person[“skills”][“programming”] = “.NET”
data.push(person)
person = {}
person[“name”] = “Frank”
person[“age”] = 50
person[“skills”] = {}
person[“skills”][“programming”] = “Javascript”
data.push(person)
console.log(data)
I get the expected output:
[
{ name: ‘Bob’, age: 30, skills: { programming: ‘.NET’ } },
{ name: ‘Frank’, age: 50, skills: { programming: ‘Javascript’ } }
]
But if I run the same code but comment out resetting the person variable:
let data = []
person = {}
person[“name”] = “Bob”
person[“age”] = 30
person[“skills”] = {}
person[“skills”][“programming”] = “.NET”
data.push(person)
// person = {}
person[“name”] = “Frank”
person[“age”] = 50
person[“skills”] = {}
person[“skills”][“programming”] = “Javascript”
data.push(person)
console.log(data)
I get this …
[
{ name: ‘Frank’, age: 50, skills: { programming: ‘Javascript’ } },
{ name: ‘Frank’, age: 50, skills: { programming: ‘Javascript’ } }
]
Javascript concurrency, threading, synchronicity, it is all a mystery to me. How do I tell what is synchronous and what is asynchronous?
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0
@daveyerwinDec 05.2021 — #Javascript concurrency, threading and synchronicityare not responsible for the results of the code
you posted.
try this script ...
``<i>
</i><script>
> person = {}
> person["name"] = "Bob"
> person["name"] = "Frank"
> alert(person["name"])//alerts Frank
> copyOfPerson = person;
> copyOfPerson['name']='John'
> alert(person["name"])//alerts John
> </script><i>
</i>``when copyOfPerson's name property was changed
person's name property was also changed!
WHY?
because both copyOfPerson and person both REFER to the SAME object
0
@daveyerwinDec 05.2021 — #>@nsteblay#1640181 I get this ...
>
> [
> { name: 'Frank', age: 50, skills: { programming: 'Javascript' } },
> { name: 'Frank', age: 50, skills: { programming: 'Javascript' } }
> ]
yes
you pushed a reference to an object twice
``<i>``
</i><script>
let data = []
person = {}
data.push(person)
data.push(person)
console.log(data)
person["name"] = "Bob"
person["age"] = 30
person["skills"] = {}
person["skills"]["programming"] = ".NET"
</script><i>
</i>
in chrome and edge
console.log(data)
is not executed until the execution of the block of code
console.log(data)
is contained in is through executing so when
console.log(data)
is finally executed the properties of the two references to person are already set