How to prevent keep add string to the object in JavaScript?-CodePudding

When click on run button each time Mi string adding how to prevent Result : 1000MiMi Expected result multiple time click : 1000Mi

function App() {
      let memory = [{size:1000}]
      const handleSubmit = () =>{
        memory.map((item) => {
          const manju =  item.size   'Mi'
          item.size = manju 
          return item
        })
        console.log(memory)
      }
      return (<div>
    <button onClick={handleSubmit}>Run</button>
        </div>)
    }

CodePudding user response：

If your trying to prevent item.size from repeatedly adding 'Mi' onto the end, trying using the .endsWith() method.

const handleSubmit = () => {
    memory.map((item) => {
      if (!(item.size "").endsWith("Mi")) {
          const manju =  item.size   'Mi';
      }
      item.size = manju;
      return item;
    });
    console.log(memory);
  }

CodePudding user response：

your problem is here

memory.map((item) => {
          const manju =  item.size   'Mi'
          item.size = manju 
          return item
        })

you are overwriting the value of item

instead you have to return a new value

like this

memory.map((item) => {
   return {size: item.size   'Mi'}
})

CodePudding user response：

Since you're not using the result of map() for anything, you should use forEach() instead.

To prevent multiple Mi suffixes, check if it has already been added.

const handleSubmit = () => {
  memory.forEach((item) => {
    if (!(item.size   "").endsWith("Mi")) {
      item.size  = 'Mi';
    }
  });
  console.log(memory);
}

const memory = [{size: 1000}]
handleSubmit();
memory.push({size: 500});
handleSubmit();