for循环，如果if语句javascript不能按预期工作

Question

The idea behind this code is pretty simply when some one click on the button, insert the one false value if it does not exist, to do that, i created the for loop, which check how many false value exist, and if they are less than one than insert the false value else do nothing

here is the the code

addNote(index){
    const order = this.state.order
    var j =0;
    const note=order[index].note
    for(var i =0; i<note.length; i++){
        if(note[i].display===false){j++;}
        if(j==0){note[note.length]={display:false}}
        console.log(j)
    }
    console.log(note)
    this.setState({order:this.state.order}) 
}

if you see the console log result, it is increasing the value for j for each click, than why my if statement is working for each click, it should only work if the value for j is zero, i am talking about this line if(j==0){note[note.length]={display:false}}

here is the array before any click

0:Object
        display:true
        note:"jhj"

the array after second click

0:Object
        display:true
        note:"jhj"
    1:Object
        display:false

the array after second click

 0:Object
    display:true
    note:"jhj"
1:Object
    display:false
2:Object
    display:false

Answer 1

If both if statements are inside the loop, then you will add a new entry to the array every time addNote is called. That's because j is always 0 in the first iteration of the loop and because note[0].display is true , it stays 0 . Then of course if (j==0) is true , adding a new element to the array. In other words, you are deciding whether or not to add a new entry by looking at each element individually, not together.

if they are less than one than insert the false value else do nothing

That's not what your code is doing. Your code inserts a new value if any entry has display: true . Since the first element has that, your code always adds a new entry.

The following code would do what you want (instead of the loop):

if (!note.some(item => item.display === false)) {
  note.push({display:false});
}

Which translates to "if there is not an element with display === false add a new element.