How to convert string to boolean in typescript Angular 4

问题

I know am not the first to ask this and as I mentioned in my title ,I am trying to convert string value boolean .

I have previously put some values into local storage,Now I want to get all the values and assign all to the some boolean variables .

app.component.ts

localStorage.setItem('CheckOutPageReload', this.btnLoginNumOne + ',' + this.btnLoginEdit);

here this.btnLoginNumOne and this.btnLoginEdit are string values ("true,false").

mirror.component.ts

if (localStorage.getItem('CheckOutPageReload')) {
      let stringToSplit = localStorage.getItem('CheckOutPageReload');
      this.pageLoadParams = stringToSplit.split(',');

      this.btnLoginNumOne = this.pageLoadParams[0]; //here I got the error as boolean value is not assignable to string
      this.btnLoginEdit = this.pageLoadParams[1]; //here I got the error as boolean value is not assignable to string
}

in this component this.btnLoginNumOne and this.btnLoginEdit are Boolean values;

I tried the solutions in stackoverflow but nothing is worked.

Can anyone help me to fix this .

回答1:

Method 1 :

var stringValue = "true";
var boolValue = (/true/i).test(stringValue) //returns true

Method 2 :

var stringValue = "true";
var boolValue = (stringValue =="true");   //returns true

Method 3 :

var stringValue = "true";
var boolValue = JSON.parse(stringValue);   //returns true

Method 4 :

var stringValue = "true";
var boolValue = stringValue.toLowerCase() == 'true'; //returns true

Method 5 :

var stringValue = "true";
var boolValue = getBoolean(stringValue); //returns true
function getBoolean(value){
   switch(value){
        case true:
        case "true":
        case 1:
        case "1":
        case "on":
        case "yes":
            return true;
        default: 
            return false;
    }
}

source: http://codippa.com/how-to-convert-string-to-boolean-javascript/

回答2:

I have been trying different values with JSON.parse(value) and it seems to do the work:

// true
Boolean(JSON.parse("true"));
Boolean(JSON.parse("1"));
Boolean(JSON.parse(1));
Boolean(JSON.parse(true));

// false
Boolean(JSON.parse("0")); 
Boolean(JSON.parse(0));
Boolean(JSON.parse("false"));
Boolean(JSON.parse(false));

回答3:

In your scenario, converting a string to a boolean can be done via something like someString === 'true' (as was already answered).

However, let me try to address your main issue: dealing with the local storage.

The local storage only supports strings as values; a good way of using it would thus be to always serialise your data as a string before storing it in the storage, and reversing the process when fetching it.

A possibly decent format for serialising your data in is JSON, since it is very easy to deal with in JavaScript.

The following functions could thus be used to interact with local storage, provided that your data can be serialised into JSON.

function setItemInStorage(key, item) {
  localStorage.setItem(key, JSON.stringify(item));
}

function getItemFromStorage(key) {
  return JSON.parse(localStorage.getItem(key));
}

Your example could then be rewritten as:

setItemInStorage('CheckOutPageReload', [this.btnLoginNumOne, this.btnLoginEdit]);

And:

if (getItemFromStorage('CheckOutPageReload')) {
  const pageLoadParams = getItemFromStorage('CheckOutPageReload');
  this.btnLoginNumOne = pageLoadParams[0];
  this.btnLoginEdit = pageLoadParams[1];
}

回答4:

Define extension: String+Extension.ts

interface String {
  toBoolean(): boolean
}

String.prototype.toBoolean = function (): boolean {
  switch (this) {
    case 'true':
    case '1':
    case 'on':
    case 'yes':
      return true
    default:
      return false
  }
}

And import in any file where you want to use it '@/path/to/String+Extension'

回答5:

Boolean("true") will do the work too

来源：https://stackoverflow.com/questions/52017809/how-to-convert-string-to-boolean-in-typescript-angular-4